Coasts doi: 10.3390/coasts6030030

Authors: Randall W. Parkinson Leonard J. Scinto Oluwatosin Orimolade Lesmes A. M. Jerez Piero R. Gardinali Milena Ceccopieri

The Lake Worth Lagoon is an urban subtropical estuary impaired by discharge conveyed through the C-51 canal. To date, the origin of impairment has not been rigorously demonstrated. This study successfully applied a balance-of-flow framework to identify the predominant water source(s) conveyed to the S5A Complex, located at the headwaters of the C-51 canal. The results reveal distinct seasonal differences. During the dry season, water delivered to the S5A Complex was predominantly derived from Lake Okeechobee. During the wet season, agricultural runoff was the predominant source. Over the duration of the study, S5A Complex water management operations released 72% of the annual flow into the C-51 canal during the dry season. During the wet season, the predominant source of water flowing through the C-51 canal was locally derived from urban stormwater runoff. These findings contradict previous studies that have reported that Lake Worth Lagoon pollutant loads are derived from wet-season agricultural runoff. The analysis also revealed that recent construction upgrades designed to improve the quality of water released to the northern Everglades have (1) reduced the volume of lake water delivered to the S5A Complex during the dry season and (2) created a novel water source that, at times, contributes substantially to the S5A Complex. The results of this study deviate substantially from the currently accepted paradigm regarding the origin of Lake Worth Lagoon impairment, thus affirming the value of the periodic reassessment of adaptive management plans to ensure resource management and restoration strategies are based upon the best available information.

Coasts doi: 10.3390/coasts6030029

Authors: Francesco Scarton Mauro Bon Roberto G. Valle

Coastal lagoons are key wintering habitats for waders, yet long-term changes in their community structure remain poorly understood in Mediterranean systems. We analyzed a 30-year dataset (1993–2022, excluding 2021) of wintering waders in the Venice Lagoon to assess trends in abundance, community structure, thermal composition and spatial patterns. Total abundance increased significantly (+3.5% yr−1), while species richness ranged between 12 and 21 species per winter and increased over time. Community structure changed markedly, but the assemblage remained highly dominated by Dunlin Calidris alpina without evidence of increasing dominance or declining evenness. Instead, richness, Shannon diversity and Pielou’s evenness increased, whereas Berger–Parker dominance declined slightly but significantly. Species-level analyses showed a prevalence of increasing trends: ten of the 19 species analyzed increased significantly, three declined, one was stable, and five showed uncertain trends. Multivariate analyses based on Bray–Curtis dissimilarities showed significant compositional differences among approximately decadal periods, both including and excluding Dunlin, indicating that long-term assemblage reorganization was not solely attributable to the dominant species. The Community Temperature Index (CTI) increased significantly (p = 0.001), but this abundance-weighted signal was weak in biological magnitude and contrasted with a declining presence–absence CTI; moreover, this pattern was not robust to the exclusion of Dunlin, indicating dominance-driven dynamics. Spatial analyses revealed a strong increase in the proportion of counted birds recorded in the open lagoon (p < 0.001) and a decline in fish farms (p < 0.001), but this pattern disappeared after excluding Dunlin, suggesting that the apparent spatial redistribution was largely driven by this species. Overall, the assemblage is increasing and compositionally reorganized, while remaining strongly influenced by Dunlin dominance, highlighting the need to integrate species- and community-level approaches when interpreting ecological indicators.

Coasts doi: 10.3390/coasts6030028

Authors: Anastasios Stamou Georgios Mitsopoulos Georgios Tzanes Athanasia Tatiana Stamou Dimitrios Vakondios Konstantinos V. Varotsos Christos Giannakopoulos Athanasios Tsilimigkras Aristeidis Koutroulis Evangelos Leivadiotis Aris Psilovikos

Mediterranean islands face increasing climate risks from rising temperatures, prolonged droughts, extreme precipitation, and sea-level rise, while seasonal tourism intensifies water and energy demand during the most vulnerable periods of the year. This study examines whether incorporating tourism as an intrinsic component of the Water–Energy–Food nexus changes the assessment of climate risks in desalination-dependent island water systems. To address this question, the Water–Energy–Food (WEF) nexus is extended to Water–Energy–Food–Tourism (WEFT) and integrated into an EU-aligned Climate Risk and Vulnerability Assessment framework. The approach is applied to the Hermoupolis Water Supply System on Syros Island, Greece, where potable water supply depends largely on energy-intensive desalination. A technically bounded climate risk assessment is compared with a WEFT-adjusted assessment that accounts for tourism-driven demand amplification and water–energy interdependencies while keeping hazard exposure and likelihood climate-driven. The results show that heatwaves constitute the dominant near-term risk because they coincide with peak water demand and high electricity requirements for desalination. When tourism amplification is included, drought-related risks shift from medium to high already in the near future for key production and pumping components, indicating earlier emergence of critical risk conditions without changes in hazard probability. Coastal risks become more important toward the end of the century, especially under high-emission scenarios. The main contribution of the study is to show that tourism-driven amplification can be operationally incorporated into sensitivity and impact assessment while preserving comparability with a conventional CRVA. The proposed WEFT–KTM framework provides a transferable basis for assessing and prioritizing adaptation in desalination-dependent, tourism-driven Mediterranean island systems.

Coasts doi: 10.3390/coasts6030027

Authors: Polina Lemenkova

French coastal systems are characterized by strong environmental gradients and increasing anthropogenic pressures, resulting in rapid land cover transformations across coastal landscapes. This study investigates land cover dynamics along the northern, western, and southern French coasts using Sentinel-2 summer image time series acquired between 2015 and 2025. The research aims to identify the most dynamic coastal regions and determine where land cover transitions are most pronounced. A harmonized workflow was developed in GRASS GIS for preprocessing Sentinel imagery, generating seasonal composites, classifying land cover using a Random Forest (RF) supervised algorithm, and detecting changes through time. All imagery was processed using CORINE Land Cover (Level 1) classification nomenclature and projected to Lambert-93 (EPSG:2154). Comparative analyses were performed among the three coastal regions using statistical indicators of change intensity, persistence, and transition rates. The results reveal substantial regional differences in coastal dynamics, with the southern Mediterranean coast exhibiting the highest transformation rate (22.9% of total area changed, at 2.29% yr−1), followed by the northern English Channel coast (18.6%; 1.86% yr−1) and the western Atlantic coast (14.2%; 1.42% yr−1). Urbanization and natural vegetation loss were identified as dominant transition types across all regions. The study demonstrates the effectiveness of Sentinel-2 time series and open-source GRASS GIS methods for long-term coastal monitoring and provides a reproducible framework for large-scale assessments of coastal land cover dynamics in Europe.

Coasts doi: 10.3390/coasts6030026

Authors: Kanokporn Kaewsong Jetsada Wongprom Adisak Ngiamsanoi Surinthon Bunrod

Microplastic contamination is a growing environmental concern in coastal ecosystems, particularly on recreational beaches where human activities may influence plastic inputs. This study investigated microplastic abundance and particle characteristics across five recreational zones along Hatwanakorn Beach in the Gulf of Thailand, focusing on fine-scale variability within a spatially continuous beach system and across management regimes. Supratidal sediments were collected using a quadrat-based approach, and polymer types were identified using Fourier Transform Infrared spectroscopy (FTIR). Fibers were the predominant particle type, followed by fragments, and most particles were classified as large microplastics (1–5 mm). Significant spatial differences in abundance were observed among recreational zones (Kruskal–Wallis test, χ2 = 13.37, p = 0.0096). At the management regime scale, a negative binomial generalized linear model also indicated significant differences (χ2 = 30.58, p < 0.001), with higher abundance in the Hatwanakorn Forestry Research and Student Training Station (HWK Station) and Community regimes than in the National Park regime. These results indicate that microplastic distribution can be spatially heterogeneous even within a continuous recreational beach system, underscoring the importance of accounting for fine-scale spatial variability when assessing microplastic contamination in coastal environments.

Coasts doi: 10.3390/coasts6020025

Authors: Luis Valderrama-Landeros Samuel Velázquez-Salazar Francisco Flores-de-Santiago

Coastal zones are dynamic interfaces where land, ocean, and atmosphere interact, making them sensitive indicators of environmental change. However, quantifying shoreline movement across long distances and over multi-year timescales remains challenging using traditional ground-based methods alone. We conducted an analysis of environmental factors and shoreline dynamics along a 58 km stretch of the arid Cabo Pulmo shoreline in Mexico from 2020 to 2026 using the CoastSat tool. The landscape is characterized by a diverse array of geographical features, including sandy beaches, granite cliffs, estuarine systems, and various anthropogenic structures. Results indicated a sea-level rise of 2 mm/year over the last 27 years, which is consistent with the reported range for the Pacific (1.8 to 3.8 mm/year). Notably, we observed an increasing trend of Category 4 and 5 hurricanes in the Mexican Pacific, with an average of 1 additional hurricane per decade (1950–2023). A total of 457 Sentinel-2 satellite images were used for automated analysis using the CoastSat platform, all of which were acquired under tidal conditions not exceeding 1 m. Our findings indicate that the granite cliffs show no detectable horizontal changes in the satellite images; however, their minimal vertical erosion contributes sediment to adjacent beaches. The most significant shoreline erosion was observed north of a marina breakwater, measuring −19.7 m, attributed to the disruption of littoral transport toward the southeast. In contrast, sandy beaches located in front of streams and estuaries—characterized by a lack of infrastructure (houses and breakwaters) and gentle slopes of 2° to 4°—demonstrated positive accretion of up to 5.9 m. According to the autoregressive distributed lag model, wave energy and hurricane-driven wind gusts are the primary agents of shoreline retreat, displacing sediment seaward to the continental shelf. Sea level rise exacerbates this retreat, while rainfall plays a minor but contributing role by transporting sediment during hurricanes in this arid region. This study highlights the effectiveness of CoastSat as a neural network-based tool for analyzing shoreline changes; however, we faced certain limitations, such as the absence of in situ beach profiles due to restricted access.

Coasts doi: 10.3390/coasts6020024

Authors: Rayssa Soares da Silva-Rodrigues André Luiz Machado Pessanha

For the development of conservation and management strategies, scientists often define a ‘typical’ individual from a population and act as if all members of that group are basically the same, ecologically speaking. However, studies have found that resource use can vary among individuals from the same population, often due to their life stage, and that this variation helps reduce intraspecific competition among them. In this study, the feeding habits and the degree of individual specialization in the use of food resources, determined by the individual specialization index, were analyzed for the populations of the Brazilian silverside (Atherinella brasiliensis), mojarra (Eucinostomus argenteus), and two anchovy species (Anchoa tricolor and Lycengraulis grossidens) in different estuarine habitats. A total of 3855 specimens were collected from vegetated and unvegetated areas during the rainy and dry seasons of 2014. Overall, the highest density and biomass were registered in unvegetated areas. Density differed significantly among sites for A. brasiliensis, while for anchovies it differed significantly among seasons. Species exhibited spatial segregation in feeding, with anchovies feeding primarily in the water column, while A. brasiliensis and E. argenteus were benthic feeders. Despite using similar items, benthic species showed little dietary overlap, coexisting through differential use of prey proportions. A. brasiliensis, E. argenteus and A. tricolor were generalists, with the first two showing high intrapopulational diet variation (low IS values), whereas L. grossidens was a specialist with narrower niche breadth and lower individual specialization. Corroborating the Niche Variation Hypothesis, generalist species had a higher degree of individual specialization, which may be related both to an attempt at resource partitioning and to reducing intraspecific competition.

Coasts doi: 10.3390/coasts6020023

Authors: Yessil Varinka Saenz-Aguilar María Teresa Sánchez-Salazar

Marine spatial planning instruments often exhibit a gap between regulatory design and on-the-ground effectiveness. This study examines this gap in Mexico’s marine Ecological Territory Management Programs (POETs) within the Mexican Coastal Zone (MCZ) using a novel operational analysis methodology grounded in the logic of necessary determinants 32. We propose an operability conceptualization defined as the latent functionality of a policy instrument, only realized when specific contextual prerequisites are present, shifting analytical focus from policy design to preconditions for effective functioning. Derived from doctoral research reviewing over 300 sources on Mexican ecological planning and coastal management, we identify 47 necessary determinants organized by level of government (municipal, state, federal), validated through a documentary sample of 22 sources. The MCZ encompasses 264 municipalities (154 with coastline and 110 influenced), 24,945 km of coastline (1:50,000 scale), and 10,570 km2 of continental shelf. Marine POETs operate within a complex public management system comprising over 500 legal instruments and approximately 300 public operators safeguarding the environmental rights of 25.6 million coastal inhabitants. Despite this, persistent environmental degradation and unresolved land-use conflicts point to a systemic operability deficit. We provide a transferable analytical framework for diagnosing policy implementation failures in complex coastal governance systems.

Coasts doi: 10.3390/coasts6020022

Authors: P. Subraelu Fouad Lamghari Ridouane Francois Mitterand Tsombou Maryam Alhefeiti

As they are home to numerous significant ecosystems, natural resources, and a growing population, coastal regions are among the most vital locations on Earth. This study, pertaining to the east coast of the UAE, integrates nine distinct characteristics to provide a thorough methodology for assessing integrated coastal vulnerability. Land use and land cover (LULC), nearshore bathymetry, coastal geomorphology, coastal slope, shoreline erosion and deposition, population density, wave and tide, and nearshore benthic features are important parameters that are examined. For the first time, coastal benthic features are included to assess coastal vulnerability in this region. By combining the variably weighted rank values of the nine variables, an Integrated Coastal Vulnerability Index was created, which divides the coastline into low-, moderate-, and high-risk categories. The methodology improves the precision of regional risk assessments by combining these factors with data from real-time coastal surveillance. Approximately 26.4% of the UAE’s 178 km east coast (or 47.1 km) is at high risk, followed by 17.3% (or 30.9 km) at moderate risk and 56.3% (or 100.2 km) at low risk. The offshore areas of the east coast of the UAE are prone to shoaling and tunneling effects from incoming high waves at certain areas due to the concave-shaped bathymetry and medium-range canyons present, which exacerbate storm surges or tsunamis due to the shoaling effect. For a 3 m rise in sea level, most significantly, 5.58 km2 of plantation and 14.39 km2 of residential areas will be damaged in the Kalba and Fujairah regions. Additional commercial spaces totaling 1.07 km2 will also have an impact, adding to the existing 2.59 km2 of oil bunkers in Fujairah. More than 40,000 people who live within 3.0 m of the UAE’s east coast in six separate districts—Kalba, Fujairah City, Mirbah and Qidfa, Khorfakkan, Dadna and Bidya, and Dibba—will be impacted if a tsunami wave or storm surge of three meters strikes the east coast. Our results are intended to assist government agencies, coastal planners, and policymakers in the Northeast Emirates (Fujairah and Sharjah) in creating sustainable and successful adaptation and mitigation plans for areas most vulnerable to coastal hazards. In addition to enhancing scientific knowledge of coastal vulnerabilities, this integrative method is a useful tool for making well-informed decisions in the face of shifting socio-economic and climatic situations.

Coasts doi: 10.3390/coasts6020021

Authors: Md. Shamsuzzoha Sanjida Hossain Setu Israt Zahan Oyshi Wang Lei Md. Anwarul Abedin Ayesha Akter Tofael Ahamed

Bangladesh is an extremely climate-exposed country, with erosion, accretion, tidal surges, and cyclones continuously modifying coastal districts. Shoreline change in Bangladesh is crucial for sustainable coastal management and disaster resilience. Therefore, the objectives of this research are as follows: (i) to assess accretion- and erosion-based shoreline changes of the Bangladesh delta adjacent to the Bay of Bengal for 2021–2025 using a fixed 2021 reference shoreline and a 2025 shoreline proxy extracted from Landsat 8/9 imagery, and (ii) to explore onshore change dynamics from satellite-derived NDVI, NDBI, and NDWI for 2022–2025. The study covers 14 coastal districts and integrates the 2021 baseline shoreline, Survey of Bangladesh geospatial datasets, and 17,055 Ground Reference Points (GRPs) to support geometric consistency and spatially explicit reporting at the delta scale. Three spectral indices—Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Built-up Index (NDBI)—were applied to assess vegetation health, surface water distribution, and built-up/exposed land characteristics. Results indicate spatial variability in coastal change, with 383.49 km2 of land gained through accretion and 124.12 km2 lost to erosion, resulting in a neat accretion of 259.37 km2 between 2021 and 2025; 8747.91 km2 remained geomorphologically stable. Spectral index trends show minimal inter-annual NDVI and NDWI variability, suggesting stable vegetation cover and no long-term expansion of surface water. In contrast, a slight increase in NDBI indicates localized exposure of new sediments or small-scale land-use transitions along emerging coastal zones. Spearman correlation analysis highlights consistent negative relationships between NDVI and NDWI and moderate contrasts between NDVI and NDBI, reinforcing the coexistence of vegetation recovery, water withdrawal, and sediment-driven land emergence. The novelty of this study lies in the provision of consistent, near-real-time coastal change inventory for the full ~710 km Bangladesh delta coastline by combining a common 2021 baseline shoreline with harmonized Landsat 8/9 OLI surface reflectance (2022–2025) and linked onshore spectral-index dynamics over the same period. Overall, this short-term assessment reveals a sedimentary system that is active but balanced, with accretion surpassing erosion despite cyclone-affected disturbances, underscoring the value of operational satellite monitoring for coastal management, hazard preparedness, and climate-adaptive planning.

Coasts doi: 10.3390/coasts6020020

Authors: Husni Alhan Md Salimun Mohd Fadzil Mohd Akhir Nazli Aziz Che Din Mohd Safuan Xiong-Zhi Xue Mohd Fikri Mohamad Wan Izatul Asma Wan Talaat

Marine spatial planning (MSP) has emerged as a key governance approach for managing competing uses of marine space. However, implementing MSP in federal governance systems presents unique challenges due to the distribution of authority across multiple levels of government and sectoral institutions. This study examines the governance feasibility of MSP in Peninsular Malaysia by analyzing the interaction between constitutional arrangements, as well as legal, policy, institutional, and stakeholder perspectives. The coastal districts of Kuala Terengganu and Kuala Nerus are examined as potential pilot areas for exploring MSP implementation within existing planning mechanisms. This study adopts a qualitative governance analysis based on document review and stakeholder perspectives. Relevant constitutional provisions, policy documents, and institutional mandates are analyzed using qualitative coding in ATLAS.ti and synthesized through a Thematic Analysis Matrix. The findings indicate that Malaysia possesses several governance elements necessary for initiating MSP, including the statutory spatial planning system under the Town and Country Planning Act 1976 (Act 172) and policy recognition of coastal–marine integration. However, governance responsibilities remain dispersed across administrative levels and sectoral agencies. This study proposes a governance pathway demonstrating how MSP may be incrementally integrated within existing spatial planning mechanisms, through Local Plan adaptation and strengthened institutional coordination.

Coasts doi: 10.3390/coasts6020019

Authors: Andrea Escamilla-Trejo Thelma Michelle Ruiz-Ruiz Elia Inés Polanco-Mizquez Luz María Cruz García José Alfredo Arreola-Lizárraga

Ecological risk assessment of ecosystems facing anthropogenic pressures informs coastal management. This study evaluated the ecological risk of ecosystems in two coastal municipalities in the Gulf of California, Mexico. The coastal area under study spans 175 km of coastline and includes various ecosystems, as well as the cities of Guaymas and Empalme (~160,000 inhabitants). Ecological risk was assessed by surveying the opinions of experts on local and global activities and influences (climate change), the ecological consequences of hazards, and the resilience (fragmentation) and natural recovery of ecosystems. In addition, potential synergies between human activities and the effects of climate change were identified. The results showed that the main threats are discharges of raw or poorly treated wastewater into the sea, the generation and dumping of garbage, and illegal fishing. Wastewater discharges represent the local threat that interacts most intensively with the effects of climate change. Mangroves, coastal water bodies, and rocky shores face the greatest ecological risk due to continuous exposure to anthropogenic threats, poorly planned urban growth, and industrial development. Approximately 20% of the coastal zone is estimated to correspond to the metropolitan areas of Guaymas and Empalme, where the greatest ecological risk occurs, and these represent opportunities to promote coastal management processes aimed at ecosystem restoration and planned urban development to prevent the loss of coastal ecosystem functions and the services they provide to society.

Coasts doi: 10.3390/coasts6020018

Authors: Dkawlma Tora Giorgio Fontolan Saverio Fracaros Annelore Bezzi

This study presents the first fine-scale Coastal Vulnerability Index (CVI) assessment for Togo, evaluating coastal vulnerability and risk along the country’s 50 km barrier coastline in the context of accelerating erosion, rising sea level, and growing human exposure. Using remote sensing, GIS, and a CVI framework, shoreline trend rates, beach width, land use, and the role of existing coastal defences were analysed to support risk-informed decision-making. The coastline was segmented into 99 coastal units of 500 m, and shoreline trend rates were computed using the End Point Rate (EPR) method based on multi-temporal satellite-derived shorelines spanning from 1988 to 2024. Results show strong spatial contrasts in vulnerability, with the eastern sector of the Port of Lomé, particularly a 24.5 km stretch, exhibiting high vulnerability due to persistent shoreline retreat and narrow beach widths. In contrast, the western coastline displays lower vulnerability levels. Several erosion hotspots were identified, including Baguida and Dévinkemé, where recent shoreline retreat reaches up to −12.8 m/year. Existing coastal defences locally mitigate erosion impacts, reducing the extent of highly vulnerable shoreline from 23.5 km to 15 km. The integrated risk assessment identifies 6.5 km of coastline, primarily in the eastern port area, as being at high risk due to the combined effects of erosion and dense human settlement. These results provide spatially explicit information to support integrated coastal zone management, land-use planning, and adaptation strategies in Togo.

Coasts doi: 10.3390/coasts6020017

Authors: Monique Franzen Eduardo Siegle Aldo Sottolichio Elisa H. L. Fernandes

Given the continuous expansion of global trade, coastal and estuarine environments have been increasingly modified by anthropogenic pressures associated with port development, particularly through inlet stabilization by jetties, which often causes unintended environmental changes. This study evaluates alterations in estuarine and coastal hydro-sedimentological dynamics resulting from the construction of jetties (1911–1915) in the Patos Lagoon estuary, Brazil. A calibrated and validated numerical model (TELEMAC-3D) was used to compare pre-jetties and present conditions. Results showed that the morphological changes induced by the jetties altered estuarine circulation and sediment retention mechanisms. The reduction in current velocities within the channel increased sediment trapping, decreasing sediment transport capacity towards the adjacent coast. In contrast, along the plume jet, flow acceleration enhanced offshore export of fine suspended sediments, shifting deposition from nearshore areas to deeper offshore zones. Under northeastern wind conditions, a higher potential for mud deposition near the western jetty was observed in the post-construction scenario, reflecting a change in local deposition trends. These human-induced modifications not only reorganize sediment pathways but also influence habitat distribution and deposition patterns, highlighting the importance of considering engineering structures in sustainable coastal and estuarine management strategies.

Coasts doi: 10.3390/coasts6020016

Authors: Alexandre Medeiros de Carvalho Lidriana de Souza Pinheiro Antonio Rodrigues Ximenes Neto Vanda Claudino-Sales Sérgio Rossi José Francisco Soares Lima Júnior Regimario Pereira Lima Filho Beatriz Diniz Lopes Thalya dos Santos Sousa Rivelino Martins Cavalcante

Oil spills along the northeast coast of Brazil have the potential to cause catastrophic contamination of coastal environments and their associated biota. Beyond the direct contamination processes occurring on beaches, oil can also be transported inland by tides through estuaries. In addition, wind-driven transport of oil was observed in nearly all sections studied along the coast. Therefore, this study evaluated the potential of wind to transport oil fragments inland using both direct and indirect methods, including field observations and GIS-based mapping tools. The results identified and quantified oil fragmentation processes and wind-driven transport over relatively large distances (hundreds of meters). The presence of exhumed beachrock, combined with the absence or low elevation of foredunes and the high potential for wind transport, plays a crucial role in trapping oil on the beach surface. These factors further facilitate the fragmentation and inland dispersal of oil particles, allowing them to penetrate deeper into the coastal environment. The findings underscore the importance of assessing the contamination risks posed by oil fragments as they become incorporated into aeolian and other interconnected inland systems.

Coasts doi: 10.3390/coasts6020015

Authors: Nicolas Guillou

In estuarine environments, machine learning (ML) methods have been widely applied to predict water-level variations prone to flooding. However, most studies have focused on low-frequency components driven by tides and surges, neglecting high-frequency oscillations such as seiches. This study addresses this gap by assessing the ability of ML methods to predict seiche-influenced water levels. The application was conducted in the upper Elorn estuary (France), where seiches exceeded 0.6 m in height, with first-mode periods of 45–70 min. The ML procedure relied on a series of recurrent neural networks (RNNs, LSTM, and GRUs) and was implemented in a two-step framework to separately predict (i) low-frequency water-level variations and (ii) high-frequency seiche oscillations. The model accurately reproduced low-frequency dynamics (with a coefficient of determination of 0.98) and captured a substantial portion of seiches-related variability during major events. The integration of seiches improved peak total water-level predictions, reducing the mean absolute error by 30% during tidal cycles characterized by strong seiches (amplitude exceeding 0.1 m). Furthermore, the inclusion of seiches enhanced the estimation of the highest 10% peak water levels while reducing the tendency to underestimate measurements. These findings emphasize the importance of integrating seiche-generating physical processes into ML-based forecasting frameworks.

Coasts doi: 10.3390/coasts6020014

Authors: Mark R. Jury

This study considers temperature gradients over recent decades near Trujillo, Peru, (8.15 S, 78.95 W) using high-resolution data assimilation. Statistical analyses describe a steep gradient from the cool foggy coast to the warm coastal plains below the Andes. A cross-coast transect is analyzed for seasonal changes in maximum air temperature from SENAMHI station data interpolated with satellite infrared measurements. Weather forecasts aimed at the urban area show a cool bias at higher temperatures and often under-represent the landward increase of 5 °C/10 km, induced by wind-driven upwelling and turbulent heat flux. Morning fog-stratus tends to delay diurnal heating on the beachfront, whereas, a few kilometers inland, warming occurs due to the segregating effect of channeled long-shore winds. Although seasonality is limited near Trujillo, winter exhibits the greatest variance of maximum temperature due to fluctuations of cloud albedo. Regressions of temperature time series onto meteorological fields identify that a subtropical trough/ridge pattern leads to higher winter values due to weaker upwelling, warmer sea temperatures, and reduced fog-stratus. Long-term trends for increased sea/land gradients have implications for the adaptation to climate change.

Coasts doi: 10.3390/coasts6020013

Authors: Mark R. Jury

A remote analysis of coastal sedimentation in northern KwaZulu-Natal (KZN), South Africa, describes how summer runoff and winter wave-action operate within a highly variable climate. Despite rising sea levels, the sediment flux can sustain beaches under certain conditions. Daily satellite red-band reflectivity and ocean–atmosphere reanalysis datasets were studied over the period of 2018–2025. Statistical results indicate that streamflow discharges are spread northward by oblique wave-driven currents. Sediment concentrations peak during late winter (>1 mg/L, May–October) when deep turbulent mixing (>40 m) mobilizes sand from the seabed. A case study from September 2021 revealed that ridging high-pressure/cut-off low weather patterns can simultaneously increase streamflow, wave energy, and wind power, creating a surf-zone sediment conveyor along the coast of northern KZN. Long-term climate diagnostics from 1981 to 2025 reveal upward trends in coastal runoff, vegetation, and turbidity (0.29 σ/yr) that point to an increasingly vigorous water cycle. The warming of the southeast Atlantic intensifies the sub-tropical upper-level westerlies and late winter storms over southeast Africa. These processes occur in 5–8 year cycles and drive shoreline advance and retreat, from accretion ~1 T/m and storm surge inundations up to 5.5 m. Using Digital Earth, it was noted that ~1/4 of beaches around Africa are gaining sediment while ~1/3 are eroding. Although remote information could not close the sediment budget, realistic estimates of long-shore transport in the surf-zone (>104 kg/yr/m) and on the beach (>103 kg/yr/m) were calculated. These provide an emerging explanation for the resilience of northern KZN beaches, as sea levels rise at a rate of 0.6 cm/yr.

Coasts doi: 10.3390/coasts6010012

Authors: Estela Carbonell-Garzon Angela Mateo Laura Leyva Paula Daban Jesus Troncoso Pablo Sanchez-Jerez

Human activities have driven habitat degradation and biodiversity loss in marine ecosystems, highlighting the need for strategies that reconcile food production with ecosystem restoration. Restorative aquaculture has emerged as a potential tool to enhance habitat complexity, nutrient cycling, and biodiversity. The review highlighted a global imbalance between mussel production and research on its ecological benefits, with most studies emphasizing environmental impacts rather than positive ecosystem effects. Mussel farms enhance habitat complexity and provide trophic subsidies through mussel fall-off, supporting higher abundances of crustaceans and echinoderms, including commercial species such as lobsters. Ecological effects vary with spatial scale, production type (inshore vs. offshore), substrate characteristics, and farm structure. This review highlights both the ecological benefits and potential risks, including ecological traps. Research gaps include the need for quantitative assessments and long-term monitoring. Mussel farms act as both trophic and structural facilitators, demonstrating how low-trophic aquaculture can synergistically support marine biodiversity and ecosystem resilience. Properly managed, mussel farming could transition from a food production activity to a regenerative ecological tool.

Coasts doi: 10.3390/coasts6010011

Authors: Carolina Billet Guadalupe Alonso Matías Dinápoli Walter Dragani

Satellite-derived shorelines (SDSs) are increasingly used to monitor beach morphology worldwide, yet their application remains poorly validated in microtidal environments strongly influenced by atmospheric forcing. In this study, the performance of CoastSat and CoastSat.slope using nine years of in situ beach profiles from six sandy beaches in Buenos Aires (Argentina) was evaluated. The analysis compares alternative sea level forcings—including global tidal predictions (FES2022), a regional barotropic model with meteorological forcing (MSAS), and wave setup from reanalysis products—and evaluates the effect of using locally trained classifiers on shoreline detection. The results show that locally trained classifiers markedly reduced RMSE values, from 9–21 m with the default classifier to 7–12 m with the locally trained one, while the MSAS model consistently outperforms FES2022 for sea level corrections across all sites. CoastSat.slope provided effective slope estimates for tidal corrections but tended to overestimate values relative to field data. Sensitivity tests confirmed that overestimation has a smaller impact on water level correction than underestimation, explaining why validation metrics improved when using CS.slope-derived slopes. These findings translate into actionable guidelines: (i) prioritize regional sea level models when nontidal variability is large; (ii) apply wave setup corrections cautiously in microtidal coasts; and (iii) use locally trained classifiers in heterogeneous or urbanized beaches. Overall, this study demonstrates that with appropriate parameterization, CoastSat is a reliable tool for shoreline monitoring in atmospherically forced, microtidal coasts, and its methodological insights are transferable to other low-energy, data-scarce regions worldwide.

Coasts doi: 10.3390/coasts6010010

Authors: Patricia Moreno-Casasola Andrés De la Rosa Luis Peralta Peláez Ceferino Vázquez Báez Hugo López Rosas

Urban wetlands in coastal cities are under growing strain from urban growth, climate change, and governance that is often fragmented. This study evaluates the condition of the freshwater dune lakes located in the Veracruz–Boca del Río–Medellín conurbation in Mexico, a protected corridor made up of 33 dune lakes that is increasingly pressured by urban expansion. We used an interdisciplinary approach that combined ecological monitoring, legal analysis, and participatory management tools. Fieldwork included 24 h monitoring of dissolved oxygen, measurements of Biochemical Oxygen Demand (BOD5) in representative systems, a diachronic review of the legal evolution of five Natural Protected Areas (NPAs), and community workshops to jointly design interventions. The results showed strong day–night swings in oxygen (4.0–14.8 mg/L) linked to vegetation dynamics, with nighttime hypoxia posing risks for aquatic fauna. BOD5 ranged from 4.8 to 150.3 mg/L, pointing to severe organic pollution in the most degraded system. The legal review identified repeated patterns of environmental regression, expressed through reductions in protected polygons, the legalization of irregular settlements, and the fragmentation of protected areas through judicial processes. In response, we propose a hybrid management model that brings together riparian restoration, Sustainable Urban Drainage Systems (SUDS), green infrastructure, and participatory monitoring, emphasizing a key 100 m buffer zone. This integrated strategy aims to improve flood regulation, reduce urban heat island effects, and enhance water quality, while also reinforcing community stewardship and legal protection. We conclude that conserving these urban wetlands effectively requires adaptive approaches that connect landscape-scale and local-scale actions, which are essential for climate adaptation in rapidly urbanizing coastal regions.

Coasts doi: 10.3390/coasts6010009

Authors: Cheikh Omar Tidjani Cisse Rafael Almar Mamadou Sadio

Coastal storms represent a major environmental issue and constitute an important challenge for coastal flood management. This study analyzes the frequency and characteristics of storms on the Senegalese coast between 1993 and 2023, focusing on four coastal cities: Dakar, Saint-Louis, Mbour, and Cap-Skring. The analysis is based on wave data from the ERA5 model and on meteorological and oceanographic data from different models. Storms were detected using the Peak Over Threshold (POT) method, based on the 95th percentile and fitted to a generalized Pareto distribution (GPD). The results reveal a contrasted spatial distribution of coastal storms, with a higher occurrence in Dakar and Saint-Louis. An apparent increase in the frequency of storms is observed in Saint-Louis, Mbour, and Cap-Skring, while an apparent decrease is noted in Dakar; however, these trends are not statistically significant. Extreme coastal water levels (ECWL) associated with storms show an opposite evolution, with an apparent decrease in the first three regions and an apparent increase in Dakar. The most intense and longest storms, in terms of energy content (Es), are mainly observed in Dakar and Saint-Louis. A linear relationship is highlighted between the duration and intensity of storms. Storm occurrence shows a strong seasonal modulation, with a predominance during the dry season (November to May). The most energetic storms are mostly generated by waves from the west to west-northwest direction in Dakar and Saint-Louis, while Mbour and Cap-Skring present a wider directional window. This first analysis at the scale of the Senegalese coast provides essential elements for understanding the risk of coastal storms and constitutes support for coastal flood management in a context of climate change.

Coasts doi: 10.3390/coasts6010008

Authors: Yusif Owusu Komlan Agbéko Kpogo-Nuwoklo Anthony Twum Bapentire Donatus Angnuureng

Reanalysis wave datasets are essential for understanding wave conditions along the West African coast, a region with over 350 million people and diverse economic activities. This study evaluates the effectiveness of various datasets, including ERA5, WAVERYS, satellite (HY-2B/HY-2C), and buoy measurements, focusing on significant wave height (Hs). WAVERYS was found to better match in situ conditions compared to ERA5, making it the preferred dataset for climate estimation. This study found that wave heights (Hs) of WAVERYS in the region range from 0.5 m to 3.2 m, with waves primarily coming from the south and southwest, having periods between 3.8 s and 25 s. Swell, originating from the South Atlantic Ocean, dominates the wave climate, while local wind waves contribute only about 5% to the overall sea state energy. Seasonal analysis showed that the highest waves occur between June and September, coinciding with the South Atlantic winter and stronger winds. The validation performed in this study confirms that the WAVERYS reanalysis can reliably be used as a source of wave data in the Gulf of Guinea. This recommendation is based on its consistently better agreement with the available in situ observations and its improved representation of wave dynamics in the region. At locations where buoy measurements exist, in situ data should remain the primary reference for site-specific applications; however, such measurements are spatially sparse and temporally limited across West Africa. Consequently, WAVERYS provides a practical and robust alternative for regional-scale analyses, long-term assessments, and operational applications in areas lacking direct observations, making it particularly valuable for coastal risk assessment, engineering design, and marine operations in the region.

Coasts doi: 10.3390/coasts6010007

Authors: Chinomnso C. Onwubiko Denis W. Aheto

Nature-based Solutions (NbS) have emerged as transformative approaches to address societal challenges, support biodiversity, and enhance human well-being. Globally, NbS are recognized for their potential to mitigate climate change impacts such as coastal flooding. Despite growing policy interest, limited empirical evidence exists on their real-world effectiveness, particularly in Africa. The core objective of this study was to evaluate how community perceptions, awareness, and demographic factors influence the acceptance and effectiveness of NbS for flood risk reduction in selected coastal communities of Rivers State, Nigeria. Specifically, it aimed to assess community perceptions and awareness of NbS, identify demographic, geographic, and psychosocial factors influencing these perceptions, and analyze how risk perception and local knowledge affect acceptance. The study addressed three key questions: (1) How do community perceptions affect NbS acceptance and implementation? (2) What factors shape awareness and understanding of NbS in Kula, Oyorokoto, and Bonny? (3) How do perceptions vary across demographic groups? To answer these, a structured survey of 1224 respondents was conducted: 61% were male and 39% female, with most aged 31–50 years (80%). Education emerged as a key factor—about 49% of respondents had at least secondary or post-secondary education, which showed a significant link with positive perceptions of NbS (χ2 = 460.98, p < 0.001, Cramer’s V = 0.434). Occupation also shaped views: traders (36.8%) and fishers (24.5%) formed the majority, with occupational patterns showing moderate influence (χ2 = 112.68, p < 0.001, Cramer’s V = 0.215). Overall, awareness was the strongest predictor, with communities reporting higher NbS awareness demonstrating significantly greater acceptance (OR = 0.06, p < 0.001). These findings highlight that targeted awareness-raising, education, and community engagement are critical to promoting mangrove conservation, afforestation, and ecosystem restoration, ultimately strengthening resilience to climate-induced risks in coastal communities.

Coasts doi: 10.3390/coasts6010006

Authors: Suzanne G. Ayvazian Donald Cobb Cathleen Wigand Kenneth Miller Natalie Schafer Alexandra Beardwood Sara Miller Nia Bartolucci

Shellfish restoration and aquaculture are considered as innovative methods to mitigate in-water nutrients in coastal waters. Water quality was examined at two oyster aquaculture farms in Potter (2021–2023) and Pt Judith (2023) Ponds in southern Rhode Island, USA. Twice monthly, on a flooding tide, upstream and downstream positions were established and water quality measures were made using fluorometry sondes and laboratory analysis. Significant differences in chlorophyll a, turbidity, and nutrient concentrations between upstream and downstream positions were identified; however, the differences were not consistently greater upstream or downstream. Percent Chl a removed varied from −74% to 64% at Potter Pond among years and −51% to 29% at Point Judith Pond, indicating a deficit or increase in Chl a concentration downstream as compared to upstream over each sampling period. Chlorophyll a measured inside oyster bags was higher compared to the upstream position at Potter Pond, and results from the upstream, downstream, and within farm productivity experiment in both ponds suggest oyster byproducts may facilitate localized and seasonal phytoplankton production. Natural resource managers should consider that while oyster farms in coastal ponds can provide local water clarity through removal of phytoplankton, benefits may be site specific and seasonal.

Coasts doi: 10.3390/coasts6010005

Authors: Gerasimos A. Kolokythas Athanassios A. Dimas

The three-dimensional, turbulent, free-surface flow developing in the surf zone over a constant-slope beach as a result of the interaction between the longshore current and the undertow, induced by spilling wave breaking oblique to the shoreline, is numerically simulated. The simulations are performed by implementing the large-wave simulation (LWS) method in a numerical solver of the three-dimensional Navier–Stokes equations. According to the LWS method, large velocity and free-surface elevation scales are fully resolved, while the effect of the corresponding subgrid scales is modeled by eddy-viscosity stresses. The model validation is based on the comparison between the present numerical results and existing experimental measurements for a case of incident regular waves propagating normal to the shoreline over a bed of constant slope 1/35. It is found that the LWS model adequately predicts the wave-breaking parameters—breaking height and depth—and the undertow vertical profiles in the surf zone. Then, two cases of oblique waves, with wave incidence angles of 20° and 30°, and all other parameters identical to those of the validation case, are considered. The numerical results include the gradual breaking process of the refracted waves, as well as the three-dimensional structure of the longshore current and the undertow in the surf zone. In the outer surf zone, the undertow has a larger velocity magnitude than the longshore current, while in the inner surf zone, the opposite occurs.

Coasts doi: 10.3390/coasts6010004

Authors: Francesco Scarton Roberto G. Valle

The Sacred Ibis Threskiornis aethiopicus is an invasive alien species (IAS) that has become established in many European countries. Because of its invasive status and its frequent interactions with native species, understanding the behavioural tolerance of this species to human disturbance is relevant for both conservation and management. Here, we analysed Flight Initiation Distances (FID) of T. aethiopicus recorded between 2012 and 2025 across the northern Adriatic coast. The dataset (n = 72) included approaches on foot and by boat in six habitat types (artificial saltmarshes, farmlands, brackish ponds, freshwater wetlands, saltmarshes, tidal flats). Mean FID was 41 m (SD = ± 24); it was affected mainly by group size, whereas habitat, season and approach mode had no clear effect. A cross-species analysis of mean FID versus body mass indicated that, for its size, T. aethiopicus has a much shorter FID than expected from the allometric relationship observed in 20 other waterbirds species for which FID was also collected (n = 1505) at the same sites. The results suggest partial habituation to anthropized environments and a limited flight response compared to native species. These findings may support management actions aimed at monitoring and controlling the expansion of the species while mitigating disturbance to native assemblages.

Coasts doi: 10.3390/coasts6010003

Authors: Román Manuel Vásquez-Elizondo Adrian Fagundo-Mollineda Shrinivas Nandi Daniel Robledo

This review synthesizes the literature on the degradation and decomposition of holopelagic Sargassum, with a focus on process dynamics, including microbial contribution, process descriptions, and ecological impacts. Our objective is to consolidate a robust knowledge framework to inform and optimize management strategies in affected areas. Overall, we observed that the current literature relies primarily on isolated field ecological descriptions rather than a coherent, unified research line; mechanistic studies, including bacterial pathways and factors controlling degradation, remain scarce. At the fine scale, microbial community shifts during decomposition are strongly linked to the sequential utilization of distinct organic substrates, thereby favoring the proliferation of microorganisms capable of degrading complex organic molecules and of bacterial groups involved in sulfur respiration, methanogenesis, and nutrient recycling. In the case of sulfur respiration, groups such as Desulfobacterales and Desulfovibrionales may be responsible for the reported H2S emissions, which pose significant public health concerns. At a broad scale, degradation occurs both on beaches during emersion and in the water column during immersion, particularly during massive accumulations. The initial stages are characterized by the release of organic exudates and leachates. Experimental and observational studies confirm a strong early-stage release of H2S until the substrate is largely depleted. Depending on environmental conditions, a significant amount of biomass can be lost; however, this loss is highly variable, with notable consequences for contamination studies. Leachates may also contain low but ecologically significant amounts of arsenic, posing a potential contamination risk. Decomposition contributes to water-quality deterioration and oxygen depletion, with impacts at the individual, population, and ecosystem levels, yet many remain imprecisely attributed. Although evidence of nutrient enrichment in the water column is limited, studies indicate biological nutrient uptake. Achieving a comprehensive understanding of degradation and decomposition, including temporal and spatial dynamics, microbiome interactions, by means of directed research, is critical for effective coastal management, improved mitigation strategies, industrial valorization, and accurate modeling of biogeochemical cycles.

Coasts doi: 10.3390/coasts6010002

Authors: Breno Carvalho da Silva Lucas Garcia Martins João Hemerson de Sousa Yedda Christina Bezerra Barbosa de Oliveira Rômulo Romeu Nóbrega Alves

Incidental capture (bycatch) is a major threat to all seven marine turtle species worldwide. This systematic review assessed (i) research trends over the past 20 years; (ii) relationships between fishery types, gear, and species caught; (iii) post-capture outcomes; and (iv) challenges in bycatch mitigation. A systematic search of Web of Science and Scopus up to April 2024 identified 236 studies, comprising 336,616 global bycatch records. Publications on turtle bycatch increased significantly (p < 0.001), peaking in 2020. Reported captures also rose (ρ = 0.45; p = 0.026), with Caretta caretta most frequently documented (74.8%). Methodology influenced outcomes: aerial monitoring and direct observation underestimated captures of Chelonia mydas, Lepidochelys kempii, and Eretmochelys imbricata compared with mixed methods; interviews only affected the latter. Regarding fishery interactions, Dermochelys coriacea was more susceptible to hook-and-line fishing (p = 0.0079), while C. mydas was more associated with small-scale fisheries (p = 0.0115). Most turtles were released after capture (60.6%), with no significant temporal variation in outcomes (p > 0.05). Despite growing monitoring, knowledge gaps remain in standardized reporting, regional and species coverage, and methodological integration. Addressing these issues is essential to guide effective, collaborative conservation strategies.

Coasts doi: 10.3390/coasts6010001

Authors: Wonder Adzigbli Julian Bloomer John Morrissey

The study focuses on the impact of climate change and spatial planning policies on coastal landscape dynamics. We examine the present and future coastal land use/land cover (LULC) change for southwestern Ghana under the coastal resilience (CR) scenario and coastal planning (CP) scenario. It employs an integrated approach of a review of literature and satellite imagery analysis to map coastal land use/land cover (LULC) change, from 2010 to 2020, to predict future landscape transitions under a coastal resilience approach and then contrast it with a scenario where development of the coast continues. The results show a continual decline in wetlands, from 1882.43 ha in 2010 to 1743.49 ha in 2020. Increased development would dominate the landscape under a scenario where coastal planning continues to expand, whereas cultivated, agricultural lands and vegetation are likely to increase under a coastal resilience scenario in 2035 and 2057. This study recommends that government and other stakeholders should consider coastal landscape restoration plans and programmes towards landscape sustainability for Sustainable Development Goals (SDG) 11 and 13.

Coasts doi: 10.3390/coasts5040049

Authors: Ana Beatriz A. de M. Salata Marília G. A. Pereira Isabelle F. S. de Lima Ignes Regina dos Santos Danielle M. M. Franco Boniek G. Vaz Jandyson M. Santos

Brazil suffered the largest oil spill disaster in its history, beginning on August 2019, affecting the Northeast coast. This study proposes a chemical investigation of oils from the 2019 spill in Brazil, which had naturally undergone different weathering processes in terrestrial and aquatic environments after an extended period of exposure. Three samples were collected at different times and under distinct environmental conditions, coded as spilled oil (SO), oil recovered from the aquatic environment (SA), and oil collected from the terrestrial environment (ST), the latter two having spent more time naturally exposed to aquatic and terrestrial environments. The analyses were performed by gas chromatography–mass spectrometry (GC-MS) and electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results of the GC-MS analysis indicated that, although the samples share a common geochemical origin, the SA and ST samples showed a decrease in the intensity of n-alkane distribution compared to the SO sample, mainly attributed to evaporation and biodegradation processes. FT-ICR MS analysis identified dozens of classes of ESI(+) and ESI(–) compounds, most of them rich in sulfur and oxygen, with the highest intensities and quantities of molecular formulas in the SA and ST samples. Diagnostic ratios for heteroatom classes concluded that the SA and ST samples had undergone a higher level of weathering, mainly associated with photooxidation and biodegradation processes. Thus, the combined use of GC-MS and FT-ICR MS proved to be a robust approach for the detailed characterization of spilled oils, contributing to a clearer understanding of the extent and type of weathering in samples from the 2019 Brazilian spill.

Coasts doi: 10.3390/coasts5040048

Authors: Juan Carlos Alcérreca-Huerta Oscar F. Reyes-Mendoza Laura Carrillo Mariana E. Callejas-Jiménez Viridiana González-Garduño

Unprecedented quantities of pelagic sargassum since 2011 have demanded technical and management responses. Inappropriate measures might worsen environmental impacts, particularly in low-income regions and protected natural areas that also require low-cost, socio-ecologically integrated alternatives. This study aims to evaluate the effectiveness and local perception of sargassum clean-up treatments developed through a community–academic collaboration within a socio-ecological systems framework in the marine protected area Xcalak Reefs National Park (PNAX), at the southernmost Mexican Caribbean coast. In 2019 and 2021, clean-up efforts were implemented through the national PROREST program and a self-organized community group of 35–40 members supported by a multidisciplinary research advisory team. Monitoring in 2021 estimated sargassum removal at 4012 m2 over 50–75 work hours. Although average shoreline retreat was obtained (δmean = −0.22 m), final accretion of ~0.96 m alleviated community concerns about erosion linked to clean-up activities. The most effective and socially accepted clean-up treatment involved sargassum spreading, collection, drying, and revetment-type beach protection, reducing odors and harmful fauna. However, treatments aimed at shoreline stabilization were impractical, raising doubts about their long-term efficacy. These findings highlight the relevance of integrating ecological performance and social perception in sargassum management, especially where co-management with local communities in marine protected areas is needed.

Coasts doi: 10.3390/coasts5040047

Authors: Trevor Tubbs Robert Smith Adam Catasus Puspa Adhikari James Douglass Hidetoshi Urakawa

Microbial communities play a crucial role in coastal ecosystem function, yet their seasonal and spatial dynamics in response to environmental change remain underexplored in tropical and subtropical regions. This yearlong study investigated microbial composition in water, sinking particles, and sediments along an inshore–offshore gradient influenced by the Caloosahatchee River Estuary in southwest Florida. The region has been altered by rapid coastal development and was struck by Hurricane Ian in September 2022. Environmental parameters exhibited significant spatiotemporal variation, shaping microbial beta diversity in all habitats. Sediment communities showed the greatest hurricane-induced disruption but returned to pre-disturbance conditions within six months. Dominant microbial classes included Alphaproteobacteria, Bacteroidia, and Gammaproteobacteria. Biogeochemical cycling taxa displayed strong habitat specificity, such as Desulfobulbia which dominated sinking particles, Desulfobacteria which was abundant in sediments, and Nitrosomonadaceae and Nitrosopumilaceae which were key nitrifiers in water and sediments, respectively. Particle–sediment taxonomic overlap suggests resuspension processes. Several inshore microbial indicators were consistently present across microbial habitats, especially at estuarine sites, suggesting the estuary as a microbial diversity reservoir for the coastal zone. These results highlight the value of long-term microbial monitoring to understand ecosystem change and resilience in dynamic coastal environments.

Coasts doi: 10.3390/coasts5040046

Authors: Mayara de Oliveira Bandeira Caroline Fiório Grilo Kyssyanne Samihra Santos Oliveira Alex Cardoso Bastos Valéria da Silva Quaresma

The erodibility of natural cohesive sediments and artificial mixtures was investigated through controlled laboratory experiments and used as a basis to discuss seabed mobility and suspended particulate matter on the Continental Shelf adjacent to a river mouth. Changes in the erodibility of cohesive seabeds can influence resuspension and erosion rates and impact suspended particulate matter dispersion patterns and even the benthic community. For the experiments, sediment samples with sand content ranging from 0% to 90% were tested using an erosion testing chamber to evaluate the relationships among sand content, settling, consolidation, critical shear stress, and erosion rate. Critical shear stress values ranged from 0.31 to 0.42 N/m2, and erosion rates varied up to 30 times between the most mud-rich and sand-rich samples. Natural samples exhibited lower erodibility, evidenced by higher critical shear stress and lower erosion rates compared to Industrial Clay, highlighting the role of organic matter in enhancing sediment stability. Additionally, although the sand addition reduced the critical shear stress required for sediment motion, it resulted in lower erosion rates. Results were also compared with sediment samples collected from the Continental Shelf adjacent to the Doce River mouth, a region impacted by a large-scale mining tailings spill in 2015. Although the frequency of sediment mobilization did not differ significantly between pre- and post-disaster conditions, mud-rich sediments exhibited greater erosion potential once the threshold was surpassed. This suggests that the dam failure impacted the sediment dynamics of the Continental Shelf adjacent to the Doce River mouth. These findings can be used to improve sediment transport models and environmental management strategies in disturbed coastal systems.

Coasts doi: 10.3390/coasts5040045

Authors: Omar A. Alharbi Abdoul Jelil Niang

The coastline is a constantly evolving boundary between land and sea, shaped by natural forces and human activities. Given its significant ecological and economic value, this zone faces increasing pressures, highlighting the need for continuous monitoring and improved understanding to support sustainable management. This study analyses the spatial and temporal changes along the Al Qunfudhah coastline from 1984 to 2020. Using a combination of multi-temporal Landsat satellite images and geographic information system tools—specifically the digital shoreline analysis system—the research tracks changes over time. Shoreline positions were accurately extracted using automated methods, particularly the Canny edge detection algorithm. Over the 36-year period, analysis using the linear regression rate (LRR) and end point rate (EPR) methods revealed a general pattern of slight shoreline advancement. The highest rates of accretion were recorded at 12.43 m/year (LRR) and 13.36 m/year (EPR), with average rates of 3.63 m/year and 4.17 m/year, especially in the northern region where a corniche road was developed along the coast. Conversely, the most significant erosion occurred near the boat port, with maximum rates reaching −24.4 m/year (LRR) and −20.9 m/year (EPR) and average rates of −1.23 m/year and −1.08 m/year. These results offer valuable insights into the factors driving coastal changes and provide a scientific foundation for making informed, sustainable decisions about the future of the Al Qunfudhah coastline.

Coasts doi: 10.3390/coasts5040044

Authors: Fabiola Ivette Juárez-Chávez Thelma Michelle Ruiz-Ruiz Elia Inés Polanco-Mizquez Nathaly Salas-Mejía José Alfredo Arreola-Lizárraga

When designing spatial planning programs for processes in coastal zones, it is essential to consider the connections between marine and terrestrial environments and to coordinate institutional work in their implementation. This study examines the environmental policies of two planning processes in the coastal zone, one terrestrial and one marine, which were formally developed and adopted through decrees in the State of Sonora (NW Mexico). The Gulf of California Marine Spatial Planning (MSP-GC) was decreed in 2006, and the Sonora Coast Land Spatial Planning (LSP-SC) was decreed in 2009 and updated in 2015. This study reviewed, compared, and spatially analyzed the environmental policies established by both planning processes. The results show that both planning processes contain environmental policies with limited links between the marine and terrestrial environments in practice. Both planning processes were enacted with effort, resources, and stakeholder participation, but have not been implemented effectively. It is essential to review the mandates of the decrees, conduct an integrated assessment of environmental policies, and seek ways for federal and State institutional structures to drive the implementation of these planning processes. Considering the dates of the MSP (2006) and LSP-SC (2015) decrees, now it is the right time to evaluate them.

Coasts doi: 10.3390/coasts5040043

Authors: Giuliana Marletta Andrea Lombardo Donatella Serio Anna Maria Mannino

This study explored the occurrence, density, and distribution of Fucales along the island of Lampedusa, almost 30 years after the latest studies conducted on the marine vegetation of this island. To carry out this study, we conducted a monitoring activity in 18 sites through both scuba dives and snorkeling. During this study, a total of 13 species (three belonging to Cystoseira sensu strictu (s.s.), five to Ericaria, two to Gongolaria, and finally three to Sargassum) were observed. Nine species were previously reported, four taxa (E. brachycarpa, E. funkii, E. giacconei, and S. cf furcatum) were reported here for the first time in Lampedusa, and six species have not been found anymore. Ericaria giacconei may have always been present on Lampedusa Island, but it might have been misidentified in the past. The record on the island of Lampedusa extends the known distribution range of this species. The presence of S. cf furcatum, a non-indigenous species that is recently expanding in the Mediterranean Sea, could be considered further proof of ongoing seawater warming. In conclusion, we found that the predominant species’ association described in the past for the island of Lampedusa has remained unchanged in terms of species and biodiversity found in the studied sites. Nevertheless, we observed some changes in the Fucalean species, in particular a reduction in the canopy density values of some deep species. Therefore, we believe that the zonation pattern of the MPA should be revised, paying more attention to the conservation of fucalean species. Moreover, it will be important to manage and control the populations of the rabbitfishes, mitigating their impacts on the fucalean stands of the island.

Coasts doi: 10.3390/coasts5040042

Authors: César Mosso Manuel Viñes Carlos Astudillo Vicente Gracia Daniel González Felícitas Calderón-Vega Joan Pau Sierra Agustín Sánchez-Arcilla

The Mediterranean coast is known for its great tourist attractions, concentration of population, and economic activities. Specifically, in the autonomous regions like Catalonia and Valencia, more than half of the population lives in coastal counties, and the population during the summer months increases due to the influx of tourists. Furthermore, in this stretch of coast, there are some areas of natural interest such as the Delta del Ebro or the Albufera, which are two of the most important wetland areas in the Mediterranean. However, according to studies by Day Today, the retreat of the coastline has increased in recent years, and this influences management of coastal territory both directly and indirectly, mostly harming all sectors with low levels, creating spaces with significant problems. It is for this reason that reporting on climate change and the impact on the coasts is assuming an important role in society, because they are essential tools for planning and management costs. In this thesis, the ground that would be affected by a +1 m, +2 m, and +3 m increase in average sea level, as simulated by the existing flood simulator, has been quantified. And a methodology has been developed for determining the vulnerability of the land based on flooding provided by terrain elevations, and each area studied was evaluated with different degrees of vulnerability: very high, high, moderate, or low. Finally, a first estimate has been made of economic loss that could involve a meter rise in the average sea level for Catalan beaches, and major damage to natural parks, urban areas, and major infrastructure has been identified. This study shows that there are nine areas with high vulnerability due to the low heights of their territory, and the majority of the flooded land is concentrated in the Ebro Delta and the Albufera, which jointly dominate the totals across scenarios.

Coasts doi: 10.3390/coasts5040041

Authors: Phil J. Watson

This paper investigates the influence of back-to-back major hurricanes “Helene” and “Milton” which devastated south-eastern regions of the USA in 2024, and the extent to which associated storm surges influenced Extreme Value Analysis (EVA) of the long ocean water level record at Key West, Florida dating back to 1913. The highest recorded storm surge of 890 mm was recorded during a major hurricane event in October 1944, approximately 56 mm higher than the peak of the surge recorded at Key West during hurricane “Wilma” in 2005. Reanalysis of 2023 published EVA results for Key West indicate that despite the devastation of “Helene” and “Milton”, the super-elevation of the ocean water surface above Mean Sea Level (MSL) recorded at the Key West tidal facility during these hurricanes were at or below that which would be expected around once per annum. The timing and location of the peak of the storm surge with high predicted tides is no more than coincidental but remain the governing factors behind realizing record-breaking water levels over the historical record.

Coasts doi: 10.3390/coasts5040040

Authors: Guang Yin Sindre Østhus Gundersen Muk Chen Ong

Pipelines and power cables are critical infrastructures in coastal areas for transporting energy resources from offshore renewable installations to onshore grids. It is important to investigate the hydrodynamic forces on pipelines and cables and their surrounding flow fields, which are highly related to their on-bottom stability. The time-varying hydrodynamic forces coefficients and unsteady surrounding flows of a near-seabed pipeline subjected to a wave-induced oscillatory boundary layer flow are studied through numerical simulations. The Keulegan–Carpenter numbers of the oscillatory flow are up to 400, which are defined based on the maximum undisturbed near-bed orbital velocity, the pipeline diameter and the period of the oscillatory flow. The investigated Reynolds number is set to 1×104, defined based on Uw and D. The influences of different seabed roughness ratios ks/D (where ks is the Nikuradse equivalent sand roughness) up to 0.1 on the hydrodynamic forces and the flow fields are considered. Both a wall-mounted pipeline with no gap ratio to the bottom wall and a pipeline with different gap ratios to the wall are investigated. The correlations between the hydrodynamic forces and the surrounding flow patterns at different time steps during one wave cylinder are analyzed by using the force partitioning method and are discussed in detail. It is found that there are influences of the increasing ks/D on the force coefficients at large KC, while for the small KC, the inertial effect from the oscillatory flow dominates the force coefficients with small influences from different ks/D. The FPM analysis shows that the elongated shear layers from the top of the cylinder contribute to the peak values of the drag force coefficients.

Coasts doi: 10.3390/coasts5040039

Authors: Thaynara Raelly da Costa Silva André Magalhães Adria Davis Procópio Marcela Pimentel de de Andrade Luci Cajueiro Carneiro Pereira Rauquírio Marinho da Costa

Given the high sensitivity of small estuaries to environmental changes, the present study aimed to investigate how climate-induced stressors—particularly rainfall and salinity—affect zooplankton community structure in the Amazonian Taperaçu estuary (northern Brazil), where limited spatial scale amplifies ecological responses. This study evaluated the effects of the extremely dry 2015–2016 El Niño period on hydrological patterns and zooplankton dynamics in this shallow tropical estuary. Eight sampling campaigns were conducted, with water and zooplankton samples analyzed using standard methods. Salinity, dissolved inorganic nutrients, and chlorophyll-a concentrations were affected by the marked decrease in rainfall caused by the El Niño event. These changes significantly impacted zooplankton community dynamics, especially the densities of marine-estuarine species Acartia lilljeborgii, Euterpina acutifrons, and Oikopleura dioica, which peaked during months of highest salinity. High recruitment of copepod larval stages was also observed, with peak densities coinciding with dominant adult forms. In contrast, coastal and estuarine species such as Acartia tonsa, Pseudodiaptomus marshi, Oithona oswaldocruzi, and Oithona hebes were negatively affected by reduced rainfall. Species richness, diversity, and evenness during the El Niño period were relatively high compared to previously reported values under normal conditions in the same ecosystem. Environmental and temporal variables accounted for over half the variance in predominant taxa density, indicating that El Niño–driven changes influenced zooplankton structure over time. This suggests that El Niño may have strong impacts at the secondary trophic level, likely to cascade throughout the estuarine food web, altering its dynamics and the flow of carbon and energy through the system.

Coasts doi: 10.3390/coasts5040038

Authors: Anna Fricke Germán A. Kopprio Marianela Gastaldi Maite Narvarte Daniela Alemany Ana M. Martínez Florencia Biancalana R. David Rodríguez Rendas Mariano J. Albano Fernando J. Hidalgo Oscar Iribarne Rubén J. Lara Paulina Martinetto

Cultural eutrophication caused by human activity significantly impacts benthic ecosystems. This study investigated how different phytobenthic components—rhodophyte germlings, mesoalgal and macroalgal assemblages, and Ulva cf. lactuca—respond to nutrient enrichment in a tidal channel system in San Antonio Bay, Argentina. Two experiments were conducted: one in spring examined the interaction between nutrient enrichment (N + P, N + P + Fe) and grazing pressure on early and established algal communities, and the other in autumn assessed nutrient effects on assemblages and Ulva cf. lactuca. Results showed that early successional stages, such as germlings and mesoalgae, responded most strongly to nutrient inputs, while mature macroalgae remained largely unaffected. Significant growth of mesoalgae, with increased pigment concentrations (chlorophyll a, c, and carotenoids), occurred at the eutrophied SAO Channel in spring. Nutrient additions increased rhodophyte germlings but eventually reduced diatom-dominated mesoalgal growth. Mature macroalgae showed site-specific differences but did not respond to fertilization. Grazing effects were evident in treatments with protective cages, suggesting herbivory influences early-stage algal development. Overall, the study emphasizes the importance of the successional stage, grazing pressure, and environmental nutrient history in shaping benthic algal responses to eutrophication, offering key insights into the dynamics of coastal ecosystems under increasing nutrient stress.

Coasts doi: 10.3390/coasts5040037

Authors: Louis Zadi Anthony Soive Philippe Turcry Alaric Zanibellato Pierre-Yves Mahieux René Sabot Marc Jeannin

The aim of this work was to investigate the evolutionary mechanisms of an artificial sedimentary agglomerate formed by cathodic polarization in natural seawater during its abandonment to a natural environment. Previous studies indicate that the mineralogical evolution of the material is controlled by kinetic factors and/or the local precipitation of aragonite on the brucite surface. However, the observation of the precipitation of metastable phase precipitation during the initial immersion of this material (in powder form) has suggested the possibility of a more complex mechanism. The present study builds upon previous experimental work and includes thermogravimetric analysis and infrared spectrometry. The results are analyzed using numerical experimentation to evaluate the proposed hypotheses. Findings show that the transformation mechanism is characterized by the precipitation of metastable calcium carbonate phases. Under supersaturation conditions, these hydrated phases form on the brucite surface, limiting the mineral’s contact with the solution. The subsequent transformation of these amorphous phases into aragonite further reduces brucite–solution interaction, which explains the persistence of brucite both in the residual powder after 120 h of immersion and in the consolidated material after more than 20 years of exposure to natural seawater.

Coasts doi: 10.3390/coasts5040036

Authors: Joseph Dellicarpini Mark Borrelli Stephen T. Mague Stephen McKenna

The real-time forecast estimates of total water levels (TWL) associated with coastal storms by the Boston Office of the National Weather Service (NWS), and the analysis, identification, and field mapping of storm tide pathways (STP) by the Center for Coastal Studies (CCS) within the forecast region, has led to improved model forecasts, enhanced allocation of resources prior to storm impact (e.g., placement of flood control measures, identification of evacuation routes, development of applications to visualize and communicate threats, etc.), and increased public awareness of the practical implications of sea level rise and storm-related coastal flooding. Both NWS modeling and STP mapping are discussed here. The coupling of these methods began in 2016–2017 in Provincetown, MA, and its utility was highlighted during the new storm of record for most of southern New England, a nor’easter in January 2018. The use of this information by managers, stakeholders, and the public has increased since combining the TWL modeling and STP mapping in an online portal in 2021, and it continues to be used by emergency managers and the public to plan for approaching coastal storms.

Coasts doi: 10.3390/coasts5030035

Authors: Bryan A. Oakley Emily Watling Nina Musco Michael Bradley Alan Desbonnet Peter V. August Daniel T. Cole

Eelgrass (Zostera marina) is a native perennial marine angiosperm found in shallow bays and estuaries. Eelgrass beds are considered essential fish habitats and provide an important food source for marine organisms and waterfowl. This study examines changes in extent of the eelgrass beds in the southern portion of the Little Narragansett Bay Estuary, Rhode Island/Connecticut, USA, between 2019 and 2022. The primary dataset used to delineate eelgrass beds was side-scan sonar coupled with underwater video imagery. Previous studies showed a decline in the extent of eelgrass here between 2012 and 2016. Our results show an increase in eelgrass coverage from 0.52 km2 in 2019 to 0.75 km2 in 2022. This increase in the extent of eelgrass occurred against the trends of declining eelgrass coverage both globally and regionally.

Coasts doi: 10.3390/coasts5030034

Authors: Elizabeth Basha Stephanie N. Vaughn Jacqueline C. Pavlovsky Hays Roth Colin R. Jackson

Despite being low-resource environments, sandy beaches can contain diverse bacterial assemblages. In this study we examined the spatial heterogeneity of bacterial communities in sand on a beach on the Mississippi Gulf Coast, USA. 16S ribosomal RNA gene sequencing was used to characterize bacterial communities in surface sand along 10 m transects from dry sand towards the upper beach to fully submerged sand, as well as up to 0.4 m deep into the sand. There were clear gradients in bacterial community structure based on position on the beach and depth, and community richness and diversity was greater in moist sand subject to tidal influence than drier sand. Bacterial communities in sand higher up the beach were characterized by members of the phyla Bacillota and Actinomycetota, whereas there was an increased presence of picocyanobacteria (phylum Cyanobacteriota) in sand closer to the water and greater diversity overall. Along with gradients in community structure, microbial activity also showed spatial patterns, with microbial extracellular enzyme activity being greatest in surface sand at intermediate positions along the beach transects that were subject to tidal influences but not fully submerged. This research supports the idea of beaches containing diverse bacterial communities and demonstrates that the existence of gradients in beach environments means that these communities show clear patterns in their spatial distribution.

Coasts doi: 10.3390/coasts5030033

Authors: I Gede Agus Novanda Martiwi Diah Setiawati I Putu Sugiana I Gusti Ayu Istri Pradnyandari Dewi Anak Agung Eka Andiani Made Wirakumara Kamasan Putu Echa Priyaning Aryunisha Abd. Rahman As-syakur

Remote sensing offers an effective alternative for estimating mangrove carbon stocks by analyzing the relationship between satellite pixel values and field-based carbon measurements. This research was carried out in the mangrove forests of western Bali, Indonesia, encompassing three areas situated in a non-conservation mangrove forest area. This study assessed 32 remote sensing vegetation indices derived from Sentinel-2 satellite imagery to identify the optimal model for quantifying the above-ground carbon (Cag) content in mangrove ecosystems. Field data were collected using stratified random sampling and were used to develop regression models linking the Cag with vegetation indices. The Simple Ratio (SR) index exhibited the highest correlation (r = 0.847, R2 = 0.707), while the Three Index Vegetation Above-Ground Carbon (TrIVCag) model, combining the SR, Specific Leaf Area Vegetation Index (SLAVI), and Transformed Ratio Vegetation Index (TRVI) indices, achieved the best performance (r = 0.870, R2 = 0.728). The model validation results confirmed the reliability of the TrIVCag model, as indicated by a correlation of 0.852 between the model estimates and measured Cag values from independent field data. In 2023, the mangrove area in western Bali (excluding West Bali National Park) was estimated at 376.85 ha, with a total above-ground carbon stock of 34,994.55 tonC/ha. Region A had the highest average Cag at 98.97 tonC/ha, followed by Regions B (66.58 tonC/ha) and C (86.98 tonC/ha). This model offers a practical and scalable approach to carbon monitoring and is expected to play a valuable role in supporting blue carbon conservation efforts and contributing to climate change mitigation.

Coasts doi: 10.3390/coasts5030032

Authors: Andi Egon Eugene Farrell Gregorio Iglesias Stephen Nash

This study analyses the impacts of winter storms on beach response, as well as the subsequent recovery during spring and summer, at a dissipative sandy beach in Brandon Bay, Ireland. Shoreline dynamics were assessed through the integration of field data from five survey campaigns conducted between October 2021 and November 2022 with a 1D Xbeach (version 1.23) numerical model. Cross-sectional profiles were measured at seven locations, revealing pronounced erosion during winter, followed by recovery in calmer seasons, especially in the lower beach zone. The model effectively simulated short-term storm-induced morphological changes, demonstrating that rates of shoreline retreat and profile alteration are higher in the eastern bay, where wave energy is greater. Most morphological changes occurred between the low and high astronomical tide marks, characterized by upper beach erosion and lower beach accretion. Models were subsequently employed to examine future climate scenarios, including sea level rise and increased storm intensity. The projections indicated an exponential increase in erosion rates, correlated with higher storm wave heights and frequencies. These results highlight the dynamic response of dissipative beaches to extreme events and reinforce the necessity for adaptive coastal management strategies to address the escalating risks posed by climate change.

Coasts doi: 10.3390/coasts5030031

Authors: Yanlu Qiao Shuo Wang Lingzhe Wang Shijie Li Feng Wang Bo Wang Yuyang Liu

The symbiotic microbiome constitutes a consortium that has been persistently domesticated by a specific algal species, fostering a close and enduring association with the host. The majority of microbial taxa remain uncharacterized. These unknown microbes, often referred to as “microbial dark matter (MDM)”, have important ecological contributions. Given the challenges in discerning symbiotic microbes in natural environments, herein, ecological characteristics of MDM and known taxa within symbiotic communities were investigated in a simulated bloom process using Alexandrium pacificum without antibiotic treatment. Specifically, increased diversification was observed in MDM along the bloom process. Higher trophic interaction and less vulnerability of the molecular network were found in MDM taxa. The “bridge” role of MDM species was better than that of known taxa, as shown by higher betweenness centralization. Deterministic processes dominated in MDM taxa, which promote phylogenic diversity of such groups to some extent. The findings highlight that MDM taxa play an important role in sustaining community stability and functioning. This study broadens our understanding of the ecological contribution of MDM under disturbances from dinoflagellate blooms, providing essential theoretical insights and empirical data to inform the management of coastal toxic blooms.

Coasts doi: 10.3390/coasts5030030

Authors: Tahera Attarwala Amin Boukari Gulnihal Ozbay

Bivalves such as oysters rely on aragonite and calcite for shell formation via the biomineralization of calcium carbonate. Ocean acidification reduces carbonate ion availability, compromising shell growth and inducing dissolution under undersaturated conditions (Ω < 1). This study assessed the aragonite and calcite saturation state (Ω) as a proxy for evaluating habitat suitability for oyster aquaculture and restoration. Temperature, salinity, pH, and total alkalinity were monitored across multiple sites and used to calculate the aragonite and calcite saturation state via the Seacarb package. Calcium hardness and dissolved oxygen were also measured to evaluate compliance with hatchery water quality standards. Results indicated temporal and spatial fluctuations in saturation states, with frequent undersaturation during cooler months. Spearman correlation analyses demonstrated significant positive relationships between temperature and salinity (p = 0.46), between pH and aragonite saturation state (p = 0.72), and between alkalinity and aragonite saturation state (p = 0.51). These findings highlight the importance of carbonate chemistry variability and seasonal drivers in determining the suitability of sites for oyster cultivation and restoration under changing environmental conditions.

Coasts doi: 10.3390/coasts5030029

Authors: Remo Luan Marinho da Costa Pereira Luci Cajueiro Carneiro Pereira Cesar Mosso

This study aimed to evaluate how tidal modulation influences breaking waves on a macrotidal beach along the Amazonian coast under varying climatic conditions. The study utilized medium-term data (2006–2018) from national and international institutions and short-term data (2012–2014) from in situ measurements at Ajuruteua Beach. Offshore winds and waves, predominantly from the northeast, were influenced by severe storms associated with La Niña and El Niño events. During these periods, wave heights exceeded 5 m, with wave periods ranging from 12 to 20 s. Tidal fluctuations (typically 5.0–6.0 m) modulated nearshore wave heights and periods, with variations determined by offshore conditions and climatic influences. Wave heights decreased from 2–5 m offshore to 1–2 m nearshore. At low tide, sandbanks dissipated wave energy, resulting in significantly smaller breaking waves (0.1–0.5 m) compared with high tide (1–1.8 m). The northern part of Ajuruteua Beach experienced a progressive retreat, with a total area loss of 0.15 km2 and a shoreline retreat of 0.360 km between 2007 and 2021. The combination of high hydrodynamic energy and unregulated development led to the destruction of 43 buildings between 2007 and 2013 and an additional 44 houses between 2013 and 2021 within the intertidal zone. Moreover, the absence of coastal management strategies has exacerbated erosion, underscoring the urgent need for planning and regulatory frameworks. Based on the findings of this study, it is recommended that land use be regulated and both short- and long-term physical processes be systematically integrated into future coastal protection planning.

Coasts doi: 10.3390/coasts5030028

Authors: Luis Valderrama-Landeros Iliana Pérez-Espinosa Edgar Villeda-Chávez Rafael Alarcón-Medina Francisco Flores-de-Santiago

The city of Acapulco was impacted by two near-consecutive hurricanes. On 25 October 2023, Hurricane Otis made landfall, reaching the highest Category 5 storm on the Saffir–Simpson scale, causing extensive coastal destruction due to extreme winds and waves. Nearly one year later (23 September 2024), Hurricane John—a Category 2 storm—caused severe flooding despite its lower intensity, primarily due to its unusual trajectory and prolonged rainfall. Digital shoreline analysis of PlanetScope images (captured one month before and after Hurricane Otis) revealed that the southern coast of Acapulco, specifically Zona Diamante—where the major seafront hotels are located—experienced substantial shoreline erosion (94 ha) and damage. In the northwestern section of the study area, the Coyuca Bar experienced the most dramatic geomorphological change in surface area. This was primarily due to the complete disappearance of the bar on October 26, which resulted in a shoreline retreat of 85 m immediately after the passage of Hurricane Otis. Sentinel-1 Synthetic Aperture Radar (SAR) showed that Hurricane John inundated 2385 ha, four times greater than Hurricane Otis’s flooding (567 ha). The retrofitted QGIS methodology demonstrated high reliability when compared to limited in situ local reports. Given the increased frequency of intense hurricanes, these methods and findings will be relevant in other coastal areas for monitoring and managing local communities affected by severe climate events.

Coasts doi: 10.3390/coasts5030027

Authors: Chaolu Bo Miao Na Qian

Heavy metal pollution from human activities is an increasing environmental concern. This study investigates the concentrations of Cu, Pb, Zn, Cd, Hg, and As in the coastal seawater offshore of Beihai, Guangxi, in April 2021, and explores their relationships with dissolved inorganic nitrogen, phosphate, and salinity. Our results reveal higher heavy metal concentrations in the northern nearshore waters and lower levels in southern offshore areas, with surface waters generally exhibiting greater enrichment than bottom waters. Surface concentrations show a decreasing trend from the northeast to the southwest, likely influenced by prevailing northeast monsoon winds. While bottom water concentrations decline from the northwest to the southeast, which indicates the influence of riverine runoff, particularly from the Qinzhou Bay estuary. Heavy metal levels in southern Beihai waters are comparable to those in the Beibu Gulf, except for Hg and Zn, which are significantly higher in the water of the Beibu Gulf. Notably, heavy metal concentrations in both Beihai and Beibu Gulf remain considerably lower than those observed in the coastal waters of Guangdong. Overall, Beihai’s coastal seawater meets China’s Class I quality standards. Nonetheless, continued monitoring is essential, especially of the potential ecological impacts of Hg and Zn on marine life.

Coasts doi: 10.3390/coasts5030026

Authors: Rafael Schroeder Lucas Gavazzoni Carlos E. N. de Oliveira Pedro H. M. L. Marques Ewerton Wegner

Recreational diving depends on healthy marine ecosystems, yet it can harm biodiversity through species displacement and habitat damage. Bombinhas, a biodiverse diving hotspot in southern Brazil, faces growing threats from human activity and climate change. This study assessed the ecological structure of Sepultura Beach (2018) for potential diving trails, comparing it with historical data from Porto Belo Island. Using visual censuses, transects, and photo-quadrats across six sampling campaigns, researchers documented 2419 organisms from five zoological groups, identifying 14 dominant species, including Haemulon aurolineatum and Diplodus argenteus. Cluster analysis revealed three ecological zones, with higher biodiversity at the site’s edges (Groups 1 and 3), but these areas also hosted endangered species like Epinephelus marginatus, complicating trail planning. A major concern was the widespread bleaching of the zoanthid Palythoa caribaeorum, a key ecosystem engineer, likely due to rising sea temperatures (+1.68 °C from 1961–2018) and declining chlorophyll-a levels post-2015. Comparisons with past data showed a 0.33 °C increase in species’ thermal preferences over 17 years, alongside lower trophic levels and greater ecological vulnerability, indicating tropicalization from the expanding Brazil Current. While Sepultura Beach’s biodiversity supports diving tourism, conservation efforts must address coral bleaching and endangered species protection. Long-term monitoring is crucial to track warming impacts, and adaptive management is needed for sustainable trail development. The study highlights the urgent need to balance ecotourism with climate resilience in subtropical marine ecosystems.

Coasts doi: 10.3390/coasts5030025

Authors: Mark R. Jury

Coastal climate processes that affect landscape hydrology and beach dynamics are studied using local and remote data sets near Cape Vidal (28.12° S, 32.55° E). The sporadic intra-seasonal pulsing of coastal runoff, vegetation, and winds is analyzed to understand sediment inputs and transport by near-shore wind-waves and currents. River-borne sediments, eroded coral substrates, and reworked beach sand are mobilized by frequent storms. Surf-zone currents ~0.4 m/s instill the northward transport of ~6 105 kg/yr/m. An analysis of the mean annual cycle over the period of 1997–2024 indicates a crest of rainfall over the Umfolozi catchment during summer (Oct–Mar), whereas coastal suspended sediment, based on satellite red-band reflectivity, rises in winter (Apr–Sep) due to a deeper mixed layer and larger northward wave heights. Sediment input to the beaches near Cape Vidal exhibit a 3–6-year cycle of southeasterly waves and rainy weather associated with cool La Nina tropical sea temperatures. Beachfront sand dunes are wind-swept and release sediment at ~103 m3/yr/m, which builds tall back-dunes and helps replenish the shoreline, especially during anticyclonic dry spells. A wind event in Nov 2018 is analyzed to quantify aeolian transport, and a flood in Jan–Feb 2025 is studied for river plumes that meet with stormy seas. Management efforts to limit development and recreational access have contributed to a sustainable coastal environment despite rising tides and inland temperatures.

Coasts doi: 10.3390/coasts5030024

Authors: Cheikh Omar Tidjani Cisse

Today, coastal storms represent one of the most formidable environmental challenges, causing significant impacts on coastal communities. This situation underscores both the importance and urgency of studying storms and their characterization. This study proposes an innovative approach combining Principal Component Analysis (PCA) and machine learning (Classification and Regression Trees, CART) to characterize and distinguish damaging storms from non-damaging ones along the coast of Dakar, Senegal. The analysis revealed that among several hydrometeorological variables studied (wave height, period, direction, runup, wave energy, sea level anomaly, tide, etc.), the variables SLA and tide play a central role in the occurrence of damage, although they are weakly correlated with the others. By cross-analyzing these variables, critical thresholds were established, such as Tide > 0.53 m combined with SLA ≥ 0.061 m, Tide > 0.53 m and ECWL ≥ 1.3 m, as well as Runup ≤ 0.64 m associated with a high wave period (Tp), allowing accurate differentiation of potentially damaging storms. The CART method validated these results and identified three key combinations: (1) Tide–SLA, where no damage is observed if Tide < 0.53 m, and damage occurs beyond this threshold when SLA ≥ 0.061 m; (2) Tide–ECWL, where storms are damaging if Tide > 0.53 m and ECWL ≥ 1.3 m; (3) Runup–Tp, where storms are damaging if Runup ≤ 0.64 m or if Runup > 0.82 m with Tp ≥ 16 s. These results constitute the first application of machine learning for storm classification on the Senegalese coast, providing a novel quantitative foundation for better understanding the hydrodynamic conditions associated with damaging storms. The findings of this study could be valuable for risk management and the development of early warning systems

Coasts doi: 10.3390/coasts5030023

Authors: Carina Cristiane Korb Laurindo Antonio Guasselli Heinrich Hasenack Tássia Fraga Belloli Christhian Santana Cunha

Coastal wetlands play important environmental roles. However, their hydrogeomorphological dynamics remain poorly understood under scenarios of extreme climate events. The aim of this study was to characterize the temporal and spatial variability of hydrogeomorphological attributes (vegetation, water, and soil) in the wetlands of Lagoa do Peixe National Park, Brazil. The methodology involved applying Principal Component Analysis (PCA) in both temporal (T) and spatial (S) modes, decomposing spectral indices for each attribute to identify variability patterns. The results revealed that vegetation and water are strongly correlated with seasonal dynamics influenced by ENSO (El Niño/La Niña) events. Soils reflected their textural characteristics, with a distinct temporal response to the water balance. PCA proved to be a useful tool for synthesizing large volumes of multitemporal data and detecting dominant variability patterns. It highlighted the Lagoon Terraces and the Lagoon Fringe, where low slopes amplified hydrological variations. Temporal variability was more responsive to climate extremes, with implications for ecosystem conservation, while spatial variability was modulated by geomorphology.

Coasts doi: 10.3390/coasts5030022

Authors: Emanuelle Bezerra Maciel Maria Luísa de Araújo Albuquerque André Luiz Machado Pessanha

Intraspecific variations in the morphological traits of juveniles and adults of the Brazilian silverside, Atherinella brasiliensis, from three estuarine habitats were studied to understanding whether their morphology interacts with their dietary composition and habitat structure. For each individual, fourteen morphological measurements and eight functional traits were recorded related to food acquisition and locomotion. The highest abundance of A. brasiliensis was recorded in mudflats, which were often associated with a greater number of juveniles. Overall, 392 A. brasiliensis stomachs were examined, and their diet comprised mainly zooplankton organisms, followed by insects and benthic crustaceans. Among the morphological measures, our data revealed that in vegetated habitats (seagrass and riparian vegetation), individuals showed a higher oral gape surface and caudal peduncle and fed predominately on epibiotic or benthic fauna, while for individuals that had bigger eyes in unvegetated habitats (mudflat), this facilitated the ingestion of zooplankton and diatoms. Furthermore, a greater relative body height recorded in unvegetated habitats enhanced swimming performance and was linked to the effects of the lowest habitat structure. The results highlight the significant effects of morphological variation on juvenile and adult food acquisition and swimming ability.

Coasts doi: 10.3390/coasts5020021

Authors: Glaciane Marques Juliana De Biasi Carlos Hackradt Fabiana Félix-Hackradt

The Lutjanidae family includes multiple species highly important to the global fishing industry. In Brazil, approximately 40% of the fishing landings come from a species of this family, the dog snapper, Lutjanus jocu, among the most abundant in the northeast-region fisheries. This study aimed to analyze the genetic diversity and population structure of this species in the states of Bahia and Espírito Santo through the use of microsatellite markers. The dog snapper presented a high genetic variability in the studied populations, with the presence of a distinct population stock in northern Bahia probably driven by habitat suitability, larvae retention, and fishing pressure. The L. jocu sampling sites exhibited an excess of heterozygosity, a low allelic richness, and M-ratio values close to critical levels, probably indicating a recent population decline. Additionally, the low inbreeding indices and high genetic diversity values suggest a significant connectivity and considerably effective population sizes. Although these characteristics may reflect population stability, anthropogenic factors such as habitat loss, fragmentation, and overfishing may pose threats to the sustainability of the species, particularly along the northeastern coast of Brazil.

Coasts doi: 10.3390/coasts5020020

Authors: Laura Develey Leandra Gonçalves

In the context of the prevailing environmental crisis, one innovative approach with the potential to promote inclusive conservation is payment for environmental services (PES). While numerous studies have documented the efficacy of PES in terrestrial ecosystems, mechanisms tailored to marine ecosystems remain relatively unexplored. The objective of this article is to conduct a systematic literature review to identify the essential components of a PES mechanism for fisheries and to map the lessons, challenges, and opportunities associated with it. Three databases were explored: Web of Science, ScienceDirect, and Scopus. Using Boolean operators, we searched for articles containing the following terms in the title, abstract, and/or keywords: “payment for ecosystem services” AND “fish*” and “payment for environmental services” AND “fish*”. Twenty-six articles focusing in depth on PES in the context of fisheries were identified. The results indicate that PES is a tool that can reconcile conservation and social objectives while offering numerous benefits for fisheries management. Nevertheless, it is imperative to meticulously evaluate the circumstances under which PES can meaningfully contribute to the inclusive conservation of marine and coastal ecosystems rather than assuming that it is a universal policy panacea.

Coasts doi: 10.3390/coasts5020019

Authors: Francisco Uribe Mauricio Fuentes Jaime Campos

This study presents numerical simulations of the Aysén tsunami, which occurred on 21 April 2007. The tsunami was triggered by hundreds of landslides caused by a magnitude 6.2 earthquake. With an estimated wave height of 50 m at the northern tip of the Mentirosa Island, the event resulted in 10 fatalities and the destruction of multiple salmon farms along the fjord. We employed the NHWAVE and FUNWAVE-TVD numerical software to conduct a series of simulations using various landslide configurations and two approaches to model landslide motion: a viscous flow and a solid slide governed by Coulomb friction. The numerical results indicate that the solid landslide model without basal friction provides the most accurate representation of the measured in situ run-up heights and generates the largest inundation areas. Furthermore, the simulation results show that the arrival time of the tsunami waves was approximately 600 s. Our findings indicate that the volume of the landslide is the most critical factor in determining tsunami wave heights. Additionally, the Coulomb friction angle is another significant parameter to consider in the modeling process.

Coasts doi: 10.3390/coasts5020018

Authors: Almog Ben Natan Natalie Chernihovsky Nadav Shashar

With the increasing global population and migration toward coastal regions, and the rising demand for coastal urbanization, including the development of living spaces, ports, and tourism infrastructure, the need for coastal defense structures (CDSs) is also increasing. Traditional CDSs, such as breakwaters, typically composed of hard units designed to block and divert wave and current energy, often fail to support diverse and abundant marine communities because of their impact on current and sediment transport, the introduction of invasive species, and the loss of natural habitats. Marine ecoengineering aims at increasing CDS ecological services and the development of marine organisms on them. In this study, carried out in a coral reef environment, we examined the relationship between coral colony protection levels and three factors related to their development, namely, coral fragment survival rate, larval settlement, and water motion (flow rate), across three distinct niches: Exposed, Semi-sheltered, and Sheltered. Coral survivability was assessed through fragment planting, while recruitment was monitored using ceramic settlement tiles. Water motion was measured in all defined niches using plaster of Paris Clod-Cards. Additionally, concrete barrier structures were placed in Exposed niches to test whether artificially added protective elements could enhance coral fragment survival. No differences were found in coral settlement between the niches. Flow rate patterns remained similar in Exposed and Sheltered niches due to vortex formation in the Sheltered zones. Survival analysis revealed variability between niches, with the addition of artificial shelter barriers leading to the highest coral fragment survival on the breakwater. This study contributes to the development of ways to enhance coral development with the goal of transforming artificial barriers into functional artificial reefs.

Coasts doi: 10.3390/coasts5020017

Authors: Chinomnso C. Onwubiko Denis Worlanyo Aheto

Coastal habitats are crucial in mitigating the impact of coastal hazards on society. However, the shortage of information about the role of these habitats in reducing floods in Rivers State, Nigeria, is limited. This study aims to assess the contribution of mangrove habitats in protecting coastal communities from flooding using the InVEST coastal vulnerability model (version 3.10.2). The model analyzes various data inputs and assigns relative numbers, ranging from 1 to 5, indicating different levels of exposure. Data on population, bathymetry, shoreline type, land use land cover, and continental shelf were obtained from relevant websites and the InVEST model package. The findings indicate that the mangrove habitats in Rivers State offer minimal protection against coastal flooding due to their degraded state caused by oil spills and over-exploitation. Additionally, sandy beaches provide little to no protection, and the socio-economic conditions in the communities contribute to increased vulnerability to flooding. The study recommends awareness programs to educate the public about the importance of mangroves for coastal protection in addition to their conservation and restoration.

Coasts doi: 10.3390/coasts5020016

Authors: Matthew Cole Tillman Robert Marlin Smith Trevor R. Tubbs Adam B. Catasus Hidetoshi Urakawa Puspa L. Adhikari James G. Douglass

Tropical cyclones can severely disturb shallow, continental shelf ecosystems, affecting habitat structure, diversity, and ecosystem services. This study examines the impacts of Hurricane Ian on the Southwest Florida Shelf by assessing water quality, substrate type, and epibenthic and microbial community characteristics at eight sites (3 to 20 m in depth) before and after Ian’s passage in 2022. Hurricane Ian drastically changed substrate type and biotic cover, scouring away epibenthos and/or burying hard substrates in mud and sand, especially at mid depth (10 m) sites (92–98% loss). Following Hurricane Ian, the greatest losses were observed in fleshy macroalgae (58%), calcareous green algae (100%), seagrass (100%), sessile invertebrates (77%), and stony coral communities (71%), while soft coral (17%) and sponge communities (45%) were more resistant. After Ian, turbidity, chromophoric dissolved organic matter, and dissolved inorganic nitrogen and phosphorus increased at most sites, while total nitrogen, total phosphorus, and silica decreased. Microbial communities changed significantly post Ian, with estuary-associated taxa expanding further offshore. The results show that the shelf ecosystem is highly susceptible to disturbances from waves, deposition and erosion, and water quality changes caused by mixing and coastal discharge. More routine monitoring of this environment is necessary to understand the long-term patterns of these disturbances, their interactions, and how they influence the resilience and recovery processes of shelf ecosystems.

Coasts doi: 10.3390/coasts5020015

Authors: Mohsen Pourmohammad Shahvar Giovanni Marsella

This study enhances coastal vulnerability assessment by introducing a Modified Fuzzy DEMATEL technique that incorporates socio-ecological and power dynamic considerations. The novelty of the study lies in integrating causal analysis with a participatory vulnerability framework tailored to coastal management. By analyzing multiple natural and socio-economic parameters, the results identify land use and land cover as the most influential factors, highlighting a shift toward socio-economic prioritization. The model also acknowledges limitations due to reliance on expert judgment and the absence of ground-truth validation. Our findings emphasize the need for location-specific vulnerability models rather than universal frameworks, offering insights for future participatory and evidence-based coastal management strategies.

Coasts doi: 10.3390/coasts5020014

Authors: André M. Esteves Verônica S. Oliveira Paulo J. P. dos Santos Tatiana F. Maria Adriane P. Wandeness

The patterns of meiofaunal distribution in a submarine canyon and adjacent open-slope habitats at Campos Basin, southwest Atlantic, were investigated. A total of eight stations was sampled, four inside the Canyon Almirante Câmara and four on the adjacent open slope. These stations represented four isobaths (400, 700, 1000, 1300 m) and were sampled during two distinct periods (2008, 2009). At each station, three replicates were obtained and sectioned into layers of 0–2, 2–5 and 5–10 cm. Nematoda was the most abundant group in both habitats, comprising more than 85% of the total meiofauna in both sampling periods. The density and assemblage structure of the meiofauna showed high variability between the 400 m isobath and the other three isobaths in the canyon habitat. These results reinforce the roles of habitat heterogeneity and the availability of food sources as key factors strongly influencing the deep-sea meiofauna in the southwest Atlantic Ocean. Phytopigments were significantly correlated with the two major meiofaunal groups (Nematoda and Copepoda), as well as with total meiofaunal density, only in the canyon habitat. On the adjacent open slope, only copepods showed a significant correlation with sediment characteristics (mean grain size and carbonates), suggesting that distinct environmental factors influence the distribution of meiofauna in the two habitats.

Coasts doi: 10.3390/coasts5020013

Authors: Natalija Špeh Robert Lončarić

Marine litter (ML), encompassing human-made objects in marine ecosystems, poses significant threats to the coasts of some Adriatic islands, despite their remoteness and sparse populations. These islands, reliant on tourism, are particularly vulnerable to ML pollution. This study hypothesized that the natural features of the islands influence ML distribution. It employes an integrated geographic approach combining the results of field survey (via sea kayaking) with various indicators which include: (1) coastal orientation and number density of bays, (2) vegetation exposure and biomass share, (3) island area and number density of bays, (4) bay openness and ML quantity, and (5) bay openness and plastic prevalence in ML. Focusing on islands of Lošinj, Pašman, Vis, and the Kornati and Elaphiti archipelago, the study analyzed data collected over six years (2018–2023). Results highlighted that NW-SE and W-E coastal orientations are particularly susceptible to ML accumulation, especially in the southern Adriatic. Linear Fitting Regression analyses revealed a stronger correlation between number density of polluted bays and the surface area of smaller islands (<10 km2) compared to larger islands (>10 km2). The following findings underscore the need for international collaboration and stringent policies to mitigate ML pollution, ensuring the protection of Adriatic marine ecosystems and the sustainability of local communities.

Coasts doi: 10.3390/coasts5020012

Authors: Alexander F. Nielsen Angus D. Gordon

This article presents a rock armour stability formula for coastal revetments under depth-limited breaking waves that defines requisite armour mass as a function of incident wave energy. Parameters include wave height, wave period, toe depth, revetment slope, specific gravity of armour and water, percentage damage and the number of waves. The formula has been calibrated empirically based on university research flume test data. It departs from existing approaches by using wave energy in lieu of wave height as the disturbing parameter, but adopts other parameters developed by previous researchers. Results are compared with established formulae and display better coherence with the flume data. Testing constraints including possible scale effects are highlighted. Recommendations are made for further testing including the effects of seabed slope.

Coasts doi: 10.3390/coasts5010011

Authors: Vilmar Leandro Dias Ferreira Elizabeth Santos Pereira Lucas Pluvie Souza de Mello Rodrigo Amado Garcia Silva Fábio Ferreira Dias

It is estimated that around 10% of the world’s population lives in low-lying coastal areas, with an altitude of up to 10 m: considered vulnerable to unequivocal sea level rise, as result of climate change. This study sought to assess the coastal environmental vulnerabilities of the municipality of Niterói, Rio de Janeiro, Brazil, in these lowlands, through of an analysis matrix, considering sea level rise projections for 2100. The matrix was applied to nine areas along the coast and consisted of assigning values from 1 to 4 (4 being the most critical scenario) to four variables: two to natural indicators and two to socio-economic indicators. The index for each area was obtained from the simple average of the values assigned. In general, the areas facing Guanabara Bay were more sensitive in socio-economic terms, due to population densification and lower per capita income. The areas facing the Atlantic Ocean were more vulnerable in natural terms, due to exposure to waves and the presence of the natural systems protected on land located below the 10-m. These issues highlight the importance of using vulnerability analysis tools, which can enable public authorities to plan and organize the actions in each specific situation.

Coasts doi: 10.3390/coasts5010010

Authors: Yichao Tong Yuqing Sun Jing Xia Jinlin Liu

The abnormal proliferation of Ulva in the Yellow Sea has instigated the notorious green tide phenomenon. Mitigating this ecological challenge necessitates a holistic comprehension of Ulva’s nitrogen and phosphorus uptake behaviors. Investigating the mechanisms governing nutrient absorption, encompassing factors like concentration, form, and input dynamics, has unveiled their profound influence on nutrient assimilation rates. The nutrient absorption characteristics of Ulva prolifera, including its preference for abundant nutrients, a high nitrogen-to-phosphorus (N/P) ratio, and its ability to efficiently absorb nutrients during pulse nutrient input events, determine its dominant role in the green tide events in the Yellow Sea. Although source control and preemptive salvaging are effective methods for managing green tides, addressing the root causes of these coastal ecological disasters requires the implementation of long-term pollution control strategies that align with sustainable development goals, with a priority on reducing marine eutrophication. This is crucial for the effective management and restoration of the coastal ecosystem in the Yellow Sea.

Coasts doi: 10.3390/coasts5010009

Authors: Da Liu Hui Lin Xiangju Cheng Lubin Sun Lei Guo Changhong Hong

Foam pollution in the tailwater discharge from coastal power plants poses a significant challenge. However, the mechanisms underlying foam formation and stability remain understudied, which hinders the development of effective control strategies. This study investigated the impacts of temperature and algal concentration on foam stability in tailwater discharge from coastal power plants through simulation experiments to elucidate mechanisms of foam stability. A laboratory simulation device was developed to adjust temperature and algal concentration and measure foam layer height, half-life, bubble diameter, surface tension, and viscosity. This device was used to replicate foam scenarios typical of coastal power plant tailwater discharge to analyze the effects of temperature and algal concentration on foam stability through comprehensive data collection and analysis across various operational conditions. The findings revealed that foam stability decreased with increasing temperatures (15–45 °C). However, during hot summer months, higher temperatures (range of 30–40 °C) hindered foam dissipation owing to algal blooms and the release of surface-active substances. The functional relationship between foam stability index (half-life, foam layer height, bubble diameter) and temperature and algae concentration was established, which provides a scientific basis for predicting foam stability under different conditions. This research elucidates the complex dynamics of foam in the tailwater discharge from coastal power plants and provides insights for developing more effective foam control strategies, potentially mitigating adverse impacts on the marine ecosystem. In future research, by adding experimental conditions such as pH, ionic strength, and different types of protein polysaccharides, a more comprehensive understanding of the mechanism of bubble generation can be achieved, providing more accurate foam suppression optimization solutions for future engineering practices.

Coasts doi: 10.3390/coasts5010008

Authors: S. Valery Ávila-Mosqueda Brigitta I. van Tussenbroek Joaquín Rodrigo Garza-Pérez

Since 2011, recurring Sargassum Brown Tides (SBTs), caused by periodic massive influxes of holopelagic Sargassum spp., have impacted seagrass meadows in the 50–200 m wide nearshore fringes of Mexican Caribbean reef lagoons. The present study aimed to assess the cumulative effects of SBTs in 2015 and 2018–2019 through a spatial–temporal analysis of seagrass meadows in the Puerto Morelos reef lagoon. We hypothesized that the impacts of the SBTs likely extended beyond the near-shore fringe and were detectable across the seagrass landscape throughout the entire reef lagoon. Through time, the spatial configuration of the seagrass meadows presented a new self-organized configuration linked to spatial fragmentation, an increase in the number of patches but a decrease in size, and changes in vegetation communities, indicating a shift in ecosystem state. This shift may serve as an early warning signal of reef system deterioration. Monitoring seagrass meadow status using this approach provides a deeper understanding of their dynamics, shifts and resilience, and will facilitate the development of timely management strategies.

Coasts doi: 10.3390/coasts5010007

Authors: William A. Gough

A new marine climate metric, marine season, is introduced for Foxe Basin, Nunavut, Canada capturing the time of the year that the Basin is influenced by open water. The metric is developed with a day-to-day temperature variability framework using the Hall Beach (Sanirajak) climate record (1957–2023). Day-to-day minimum temperature variability provides a clear signal of the marine season. The new metric is compared to the more traditional breakup and freeze-up dates of sea ice that uses a 5/10th sea-ice spatial coverage threshold. While the two metrics are in general agreement, some important differences occur related to the time required for the breakup (full ice coverage to 5/10th sea-ice coverage). The timing from onset of the marine season to 5/10th ice coverage has shortened in time in a statistically significant fashion, indicating a more rapid breakup in recent years. In contrast, the freeze-up period, 5/10th to full sea-ice coverage has increased. The longer ice-free season, as determined by sea-ice data, arises primarily from open water changes in the breakup (shorter) and freeze-up (longer) period timing. These are novel insights that suggest that the basic sea-ice regime, oscillating from a full sea-ice platform and ice-free conditions has not changed, but rather the observed changes are in the nature of the transitions between these two states, breakup and freeze-up.

Coasts doi: 10.3390/coasts5010006

Authors: Nikolas Gomes Silveira de Souza Jader Lugon Alexandre Macedo Fernandes Ramiro Joaquim de Jesus Neves Antônio José da Silva Neto

This study addresses the challenge of identifying pollutant sources in aquatic coastal environments using inverse problem techniques hampered by particularities in hydrodynamic and Lagrangian models. An approach is presented employing the General Inverse Problem Platform (GRIPP) coupled with a General Simulated Annealing (GenSA) algorithm for robust backtracking. This methodology was applied to a hypothetical case study in Guanabara Bay, Brazil, using the MOHID Water platform for hydrodynamic and Lagrangian simulations. GRIPP significantly improved emission identification and pathway representativeness compared to traditional backtracking methods by exploring multiple potential particle origins and optimizing seeding parameters. The optimization yielded a solution with a mean error of 0.019 degrees between predicted and observed tracer locations. This demonstrates the potential of GRIPP and GenSA for solving practical environmental problems in coastal regions. The use of GRIPP can bypass eventual numerical errors in cases of long-term pollution source identification when compared to traditional methods. This approach contributes with blended models for the identification of potential sources of Lagrangian tracer emissions, as well as a potential solution to determine the pathways of pollutants.

Coasts doi: 10.3390/coasts5010005

Authors: Marcos Filho Lima Bastos Jordana Marques Kneipp Clandia Maffini Gomes Ana Paula Perlin Roberto Schoproni Bichueti

Background: By 2050, most of the global human population will live in coastal regions, and the climatic impacts on these areas represent a significant concern for governments, private sector companies, and societies. Thus, environmental management of coastal regions plays a central role in the global climate agenda. Methods: The study employed a mixed-methods approach, integrating quantitative and qualitative techniques to conduct a systematic literature review (SLR). This included the construction of networks of related topics, time series analysis, literature mapping, and the identification of research gaps. The databases used were Web of Science, Science Direct, and Scopus. The inclusion and exclusion criteria encompassed articles published between 2014 and 2023, off-topic articles, unavailable articles, or paid access articles. At the end, 96 studies were included in this RSL. Results: The results revealed a predominance of studies addressing climate management in coastal regions, primarily focused on adaptation strategies. However, there is a notable deficiency in studies that address integrated mitigation and adaptation strategies. Time series analysis predicted an increase in the focus on coastal management and climate change in the coming years. Conclusion: The research underscores the central role of coastal management in addressing climate change and achieving the Sustainable Development Goals (SDGs). It encourages multi-level management, integrating government officials, business leaders, and civil society in the development of more effective practices for climate change adaptation and mitigation.

Coasts doi: 10.3390/coasts5010004

Authors: Anderson Targino da Silva Ferreira Regina Célia de Oliveira Maria Carolina Hernandez Ribeiro Pedro Silva de Freitas Sousa Lucas de Paula Miranda Saulo de Oliveira Folharini Eduardo Siegle

Microplastics (MPs) are polymeric particles, mainly fossil-based, widely found in marine ecosystems, linked to environmental and public health impacts due to their persistence and ability to carry pollutants. In São Paulo’s northern coast, geomorphological factors and anthropogenic activities intensify the deposition of these pollutants. Through multivariate techniques, this study aims to investigate the role of the morphometrical parameters as independent variables in quantifying the distribution of MPs on the region’s sandy beaches. Using beach face slope (tanβ) and orientation (Aspect) derived from remote sensing images, calibrated by in situ topographic profiles collected through GNSS positioning, and laboratory analyses, six machine learning models Random Forest, Gradient Boosting, Lasso and Ridge regression, Support Vector Regression, and Partial Least Squares regression were tested and evaluated for performance. The Gradient Boosting model demonstrated the best performance, indicating its superior capacity to capture complex relationships between predictor variables and MPs deposition, followed by Random Forest model. Morphometric analysis revealed, once again, that in this coastal section of São Paulo, beaches with Sloping profiles oriented toward the SSW are more susceptible to MPs accumulation, especially near urban centers. Ultimately, incorporating geomorphological variables into predictive models enhances understanding of MPs deposition, providing a foundation for environmental policies focused on marine pollution mitigation and coastal ecosystem conservation while also contributing to achieve SDG 14.

Coasts doi: 10.3390/coasts5010003

Authors: Marc Bouzas Sabater Josep Burch i Rius Pere Castanyer Masoliver Ramon Julià Brugués Josep Maria Nolla Brufau Pere Pons Mir Jordi Sagrera Aradilla Joan Solà Sobiranas

The River Ter is one of the axes which, in a west-east direction, has historically articulated the population of the extreme north-east of the Iberian Peninsula. Although its upper, middle and part of the lower courses do not present any problems in its course, its mouth in the Mediterrane-an Sea has raised many questions due to the existence of two potential branches, one to the north that would flow into the Gulf of Roses and another to the south that would flow into the Bay of Pals. In 2016, an exhaustive documentary study on the potential southern branch provided exhaustive information on the existence of lake areas and their relationship with the settlement between the 9th and 11th centuries, but raised doubts about the existence of the river in the bay from Pals. Subsequently, between 2020 and 2022, geological studies have been carried out in this area which demonstrate the existence of the river in this area but with a variable course, with changes in the river channel (meandering, diffuse and braided), and with notable changes that conditioned the settlement of this sector of the coast and as was recorded in written documentation between the 9th and 11th centuries.

Coasts doi: 10.3390/coasts5010002

Authors: Catherine N. Janda Jonathan A. Warrick Daniel Buscombe Sharon Batiste

Shoreline measurement techniques using satellite-derived imagery can provide decades of observations of shoreline change. Here we apply these techniques to the western south shore of Long Island, New York, which has three distinct beaches, Rockaway Peninsula, Long Beach, and Jones Beach Island, which are 18, 15, and 24 km in length, respectively. These beaches are recreation areas for millions of regional residents and include several groin fields, sediment dredging and nourishment operations, and a coastal wave climate that includes winter northeasterly storms and summer hurricanes. The shorelines along the western ends of these three beaches have been accreting at ~4 m/yr during the observation record (1984–2022) resulting from net westward longshore drift. The central 10–12 km of the beaches have lower shoreline change rates, and these rates are generally lowest within the groin fields (0.5–1.5 m/yr). Shoreline change observations also provide evidence for westward propagating accretion and erosion sediment waves that have durations of several years. Beach nourishment projects are shown to significantly influence rates of shoreline accretion, and this is commonly followed by significant shoreline retreat during the subsequent years.

Coasts doi: 10.3390/coasts5010001

Authors: Nobuyuki Ono Takatomo Miyake Kenki Kasamo Kenji Ishimoto Toshiyuki Asano

This study investigated the thermo-hydrodynamic groundwater environment of a sandy beach where a unique sand bathing method attracts many visitors. The discussed temperatures covered a wide range, from the normal to the boiling temperature of water. We, at first, examined the feasible conditions for sand bathing and found that the volumetric water content was the crucial factor. Comprehensive field observations were implemented to elucidate two physical quantities: the groundwater flow and the temperature in the sand layer. The latter one was found to be governed by the groundwater level and tidal fluctuations. The characteristics obtained were found to be consistent with the feasible conditions in the landward area. While in the offshore area, the temperature was proved to have suddenly dropped. These results strongly suggest that the underground heat source is distributed in specific spots. A numerical model to describe the groundwater flows and the heat transfer mechanism was developed based on a saturated/unsaturated seepage flow model. The computational results were found to adequately reproduce the observed spatial temperature distribution. The reproduction ability of the model was found to be limited in terms of temporal variations; it was good for the groundwater level, but not for the temperature in the sand.

Coasts doi: 10.3390/coasts4040039

Authors: Carlos Gonçalves Tiago Verdelhos Isabel Caçador Helena Veríssimo

Salt marshes are vital coastal ecosystems, increasingly threatened by rising sea level and human pressures, that provide essential services, including coastal protection, habitat support, and carbon sequestration. This study examines the effectiveness of different eco-engineering structures in restoring salt marshes in the Mondego Estuary, Portugal, by assessing their impacts on benthic macroinvertebrate communities as bioindicators of ecosystem health. The experimental design included five experimental cells: wood palisade (Fence), geotextile fabric (Geotextile), geotextile bags filled with sand (Bags), a cell with autochthonous vegetation (Plants), and a Control cell with bare soil. Monitoring took place from 2019 to 2021, with both before and after intervention sampling to evaluate species composition, biomass, and density. Key ecological indices, such as the AZTI’s Marine Biotic Index (AMBI), Shannon-Wiener Diversity, and Pielou’s Evenness, were calculated alongside measurements of environmental variables. The results indicated minimal impacts on biodiversity, with observed variations primarily attributed to seasonal dynamics. While the wood palisade enhanced species richness and density, geotextile provided better community stability. The findings emphasize the importance of long-term monitoring, stakeholder engagement, and sustainable use of materials to optimize restoration efforts and better inform coastal management strategies in the face of climate change.

Coasts doi: 10.3390/coasts4040038

Authors: Pablo Antúnez

This paper presents a meta-analysis of mangrove area in Mexico, using linear mixed models to assess trends from 1970 to 2020. The objective is to highlight the changes in the extent of these vital ecosystems over the past five decades. The analysis reveals a concerning decline of approximately 163.33 hectares per year from 1970 to 2005. Although a rebound was observed starting in 2016—likely due to effective conservation efforts—these ecosystems continue to decline overall. The states that have shown a consistent decline in mangrove area include Campeche, Sinaloa, Nayarit, Chiapas, Veracruz, Oaxaca, Guerrero, Colima, and Jalisco. Threats to mangroves vary significantly by region. In the North Pacific, the expansion of aquaculture farms has contributed to over 60% of mangrove loss. In contrast, the Yucatán Peninsula faces challenges from urban development, oil exploitation, and road expansion. Additionally, tourism activities have severely impacted the states of Colima, Jalisco, Guerrero, and Quintana Roo. In the Gulf of Mexico, the primary threats include aquaculture, transportation routes, and hydraulic infrastructure. Based on these findings, seven action strategies for the ecological restoration of mangroves are proposed. These strategies, drawn from successful case studies and existing literature, include: comprehensive restoration initiatives, expansion of research and data sources, updates to current regulations, regulation of anthropogenic activities, inter-institutional coordination, education and awareness-raising efforts, and continuous monitoring and evaluation.

Coasts doi: 10.3390/coasts4040037

Authors: Enzo Pranzini Irene Cinelli Giorgio Anfuso

This study investigated the shoreline evolution of the Tuscany coast (Italy) from 1878–1883 to 2019. The 205 km sandy coastline, divided into 821 sectors, each one 250 m long, was analyzed to understand how human activities have altered this once-pristine coast. Sub-period analyses highlighted the impacts, both positive and negative, of various shore-protection projects. Initially, regional beaches were undeveloped and accreting, except for a few river deltas where alternating phases of erosion and accretion were observed. Coastal erosion began at deltas’ areas due to the reduction in sediment inputs and, at other areas, enhanced by the development of human settlements and tourism activities. This triggered the construction of protection structures that shifted erosion processes downdrift, a process that induced the downdrift extension of the structures (according to the “domino” effect), determining the transformation of a completely natural and resilient environment into a largely rigid one. Beach nourishment projects, mostly using inland quarries, added about 1 million cubic meters of sediment from the 1980s to 2019. Currently, 57.8% of beaches are larger than in the 1880s, 9.4% did not change and 32.8% are narrower. Overall, the Tuscan coast gained 6.5 km2 of beach surface with an average shoreline advancement of 32 m. Recent trends (2005–2019) show that 37.7% of the coast is eroding, 21.1% is stable, and 41.2% is accreting, with a total surface area increase of about 200,000 m2. The beach surface area is still increasing despite the existing reduced sediment input due to the limited sediment loss resulting from the presence of morphological cells enclosed by very prominent headlands and the absence of submarine canyons that would otherwise direct sediments to the continental shelf.

Coasts doi: 10.3390/coasts4040036

Authors: Qikun Xing Samuel J. Kim Charles Yarish

“Blue carbon” refers to the carbon sequestered by the world’s oceanic and coastal ecosystems, particularly through coastal vegetation such as mangroves, salt marshes, seagrasses, and marine macroalgae. These ecosystems play a crucial role in the global carbon cycle by serving as significant carbon sinks, absorbing carbon dioxide from the atmosphere and storing it in biomass and sediments over long periods. This study explores the use of environmental DNA (eDNA) to detect marine macrophytes and microalgae assemblages contributing to blue carbon in sediments across various coastal ecosystems. The research addresses the challenges of traditional monitoring methods by utilizing high-throughput sequencing of the 18S-V9 region amplified using eDNA from sediment samples collected at eight locations in the United States and South Korea. The results reveal a diverse array of taxa, underscoring the variability in community composition across different conditions. Notably, sites with seagrass beds and Ulva blooms showed distinct patterns in microalgal community structure. This study underscores the potential of eDNA analysis in providing comprehensive insights into the biodiversity of marine macrophyte ecosystems, thus informing conservation efforts and enhancing the understanding of marine ecological dynamics.

Coasts doi: 10.3390/coasts4040035

Authors: Andrea Lombardo Giuliana Marletta

For almost all the Sicilian islands, there are no faunistic data concerning marine Heterobranchia, which is one of the most sought-after groups of marine critters by photographers and diving enthusiasts all over the world. With the present study, carried out through underwater photography at various dive sites and stretches of coastline in the island of Marettimo, we made the first contribution to the knowledge of the marine Heterobranchia fauna present on this island of the Egadi archipelago. Through data collection, it was possible to document the presence of 43 species of marine Heterobranchia. Data analysis showed a remarkable homogeneity in the number of species between the examined sites. This is probably due to the peculiar environmental homogeneity present in the sites of this island, which are almost all rich in the presence of both benthic suspension feeders (the favorite prey of many groups of marine Heterobranchia) and environments full of crevices, grottos, and vertical walls, which are the preferred habitats of the majority of these mollusks. The higher number of marine heterobranch species found in Marettimo compared to the smaller number of species found on the other recently examined Sicilian islands (Pantelleria, Lipari, and Vulcano) is probably due to the massive presence of rich coralligenous biocoenoses and the particular hydrodynamic regime to which Marettimo is subject.

Coasts doi: 10.3390/coasts4040034

Authors: Luciana Lopes Guimarães Bárbara Faria Lourenço Fabio Hermes Pusceddu Fernando Sanzi Cortez Rafael Barreiros Kiyotani Gilmar Aparecido dos Santos Walber Toma Vinicius Roveri

Emerging pollutants, like phytoestrogens, are gaining attention in the scientific community for their impact on aquatic organisms. Nevertheless, there is a paucity of studies examining their effects on tropical aquatic species. In this context, the objective of this study was to (i) conduct chronic ecotoxicological assays with the sea urchin Echinometra lucunter with two phytoestrogens, namely genistein and daidzein (both derived from soy plant), and compare the results to the synthetic estrogen ‘estradiol valerate’; (ii) predict the potential risks of these phytoestrogens through an ecological risk assessment; and (iii) create a prioritization list of the most hazardous phytoestrogens using environmental persistence, bioaccumulation, and toxicity (PBT criteria). The results of chronic exposure demonstrated the following order of toxicity: daidzein (IC50 = 2.60 mg/L); genistein (IC50 = 3.37 mg/L); and estradiol valerate (IC50 = 28.40 mg/L). The results classify genistein and daidzein as “toxic” and estradiol valerate as “harmful” to the sea urchin. The final ranking of the PBT approach in coastal waters was as follows: biochanin A (the highest priority), followed by formononetin, genistein, enterolactone, daidzein, estradiol valerate, coumestrol, and 8-prenylnaringenin. The dataset highlights the importance of environmental monitoring to track phytoestrogens in Latin American coastal areas, particularly in developing countries.

Coasts doi: 10.3390/coasts4040033

Authors: Renato Castiglia Feitosa Paulo Cesar Colonna Rosman

The ocean disposal of wastewater is an efficient alternative in the sewage system of coastal areas since the urban density of such regions is a barrier to the settlement of conventional sewage treatment plants. In addition, the associated costs of this alternative are significantly lower than the convention in the long term. The degradation of microbiological contaminants strongly depends on solar radiation and the factors that regulate its intensity, such as the depth of the effluent plume, seasons, and cloud cover. The submarine disposal of domestic sewage constitutes a low-sanitation-risk alternative regarding the contamination of bathing areas. The results based on computational modeling corroborate this alternative, showing that the coastal zone is not affected by marine sewage discharges.

Coasts doi: 10.3390/coasts4030032

Authors: Mark R. Jury

Coastal upwelling that cools sea temperatures and nutrifies the euphotic layer is the focus of this research, motivated by how these processes benefit the marine ecosystem. Here, atmosphere–ocean reanalysis fields and satellite radiance data are employed to link South African coastal upwelling with nearshore winds and currents in the 2000–2021 period. Temporal behavior is quantified in three regimes—Benguela, transition, and Agulhas—to distinguish the influence of offshore transport, vertical pumping, and dynamic uplift. These three mechanisms of coastal upwelling are compared to reveal a leading role for cyclonic wind vorticity. Daily time series at west, south, and east coast sites exhibit pulsing of upwelling-favorable winds during summer. Over the western shelf, horizontal transport and vertical motion are in phase. The south and east shelf experience greater cyclonic wind vorticity in late winter, due to land breezes under the Mascarene high. Ekman transport and pumping are out of phase there, but dynamic uplift is sustained by cyclonic shear from the shelf-edge Agulhas current. Temporal analysis of longshore wind stress and cyclonic vorticity determined that vertical motion of ~5 m/day is pulsed at 4- to 11-day intervals due to passing marine high/coastal low-pressure cells. Height sections reveal that 15 m/s low-level wind jets diminish rapidly inshore due to topographic shearing by South Africa’s convex mountainous coastline. Mean maps of potential wind vorticity show a concentration around capes and at nighttime, due to land breezes. Air–land–sea coupling and frequent coastal lows leave a cyclonic footprint on the coast of South Africa that benefits marine productivity, especially during dry spells with a strengthened subtropical atmospheric ridge. This work has, for the first time, revealed that South Africa is uniquely endowed with three overlapping mechanisms that sustain upwelling along the entire coastline. Amongst those, cyclonic potential vorticity prevails due to the frequent passage of coastal lows that initiate downslope airflows. No other coastal upwelling zone exhibits such a persistent feature.

Coasts doi: 10.3390/coasts4030031

Authors: Robert Burns Ross Andrew Danielle Schwarzmann Mary Allen Jasmine Cardozo Moreira

Evaluating the effects of environmental events across both biophysical and social dimensions is important in establishing a holistic view of such events. This study focuses on the impact of a devastating heat stress incident that occurred in many locations across the Caribbean region and South Atlantic during the 2023 summer season. The survey and focus of data collection was within Monroe County, a unique nature-based setting south of Miami, Florida, USA. The impact of the heat wave is still being calculated at the time of submission of this paper, but indications are that there was a major negative impact. The survey and data collection sought to understand recreationists’ perceptions, knowledge, and behavior changes as result of the heat stress impact in the Florida Keys. Respondents were interviewed during community workshops in person and through an online sample of boating/angler license holders. The results indicated a change in behavior by some respondents, which may have a longer-term economic impact, along with trends of satisfaction with outdoor recreation over time. This rapid survey method can be applied to future scenarios where social and economic data are needed to fully contextualize environmental impacts in addition to biological endpoints.

Coasts doi: 10.3390/coasts4030030

Authors: Md Wahiduzzaman Alea Yeasmin

This study examines the frequency of tropical cyclones in the Bay of Bengal and their impact on Bangladesh. The extent of environmental harm led to the selection of two specific areas: the Panpatty Union and Galachipa Upzilla in the Patuakhali district, and the Sariakat Union and Swandip Upzilla in the Chittagong district. The results indicate that cyclonic storms are more common in May and November. The results also demonstrate that the studied regions are vulnerable to the effects of tropical cyclones and suffer significant consequences. The differences in influence between the two locations are statistically significant with a confidence level of 90%. The findings have significant ramifications for policymaking decisions.

Coasts doi: 10.3390/coasts4030029

Authors: Raúl R. Rodríguez-Berríos Jeremy A. Rodríguez-Vargas Francisco Colón-Cartagena Ulises Maldonado-Silva Yermarie W. Ortiz-Colón Alejandro Escalante-Castaneda Arianthony Conde-González Keiry Y. Álamo-Diverse

The coastal region of the Caribbean is notable for the chemical diversity found in its sponge products, resulting in the biosynthesis of a range of natural marine products, including polyketides. The objective of this manuscript is to summarize the isolated polyketides from sponges of the genus Plakortis located around the Caribbean coasts. This review provides a comprehensive overview of specimen location, isolation procedures, characterization methods, and biological assay studies of about 95 polyketides isolated from 1978 to 2024 in the Caribbean coasts of The Bahamas, Cayman Islands, Belize, Dominica, Jamaica, Martinique, Panamá, Puerto Rico, and Tobago. The Caribbean polyketides have been isolated from different types of Plakortis sp., such as P. simplex, P. halichondroides, P. zyggompha, and P. angulospiculatus, which have demonstrated antimicrobial, anticancer, anti-inflammatory, antiparasitic, and antiviral activities. A variety of linear polyketides with different functionalities have been reported, including endoperoxides (1,2-dioxane), lactones, indane-type bicyclics (spiculane and zyggomphic), alcohols, alkenes, styryl groups, α,β-unsaturated carboxylic acids, and ketones, as well as related natural products of biosynthetic origin. The aim is to encourage further exploration by researchers in the Caribbean’s coastal marine environments, promoting the discovery and investigation of novel polyketide cyclic peroxides and related secondary metabolites to identify additional bioactive medicinal natural products.

Coasts doi: 10.3390/coasts4030028

Authors: Rafael Schroeder Luís G. Cardoso Luciano G. Fischer Bruno L. Mourato Danielle S. Monteiro Rodrigo Sant’Ana

Endangered sharks and rays usually often lack basic information specific to conservation, such as population size. Previous studies have reconstructed shark and ray catch statistics between 1950 and 2019 for the southeast = south of Brazil, but lacking detail at the species level, because the catches were grouped by family, genus or even common name (e.g., skates and rays, Dasyatidae, Rhinobatos, Sphyrnidae, Squatinidae). In this study, we used proportions between species from scientific observer fishing trips and Dirichlet regression modelling to reclassify these categories. This model is a multivariate extension of beta regression and enables the modeling of asymmetric and heteroscedastic compositional data, allowing multinomial data to be obtained in a more informative way. The reconstruction of catches for unclassified data showed a massive dominance of the Squatinidae family until the late 1970s, when catches showed signs of decline. At the same time, the rays of the “emplastro” family showed a progressive increase from 2006 onwards. However, this scenario changed after the reclassification. The category Squatinidae was maintained almost exclusively by S. guggenheim, while 16 categories of species were observed within “emplastro” rays, many of which fall into “endangered”, “vulnerable” and “critically endangered” criteria. These reconstructed series provide a more reliable scenario of the catches of thirty elasmobranch species in the southeast and south of Brazil and serve as baseline information for understanding the conservation status of these species.

Coasts doi: 10.3390/coasts4030027

Authors: Alice Stocco Pietro Gorgosalice Marco Anelli Monti Alberto Caccin Fabio Pranovi

Recreational fishing is practiced by thousands of people in European coastal waters and is steadily gaining popularity. Serving multiple purposes, recreational fishing provides fresh fish for meals, offers leisure, and contributes to traditional ecological knowledge, especially at the local level. Therefore, analyzing its dynamics and catch is a complex task, since they not only depend on the environmental features but also on the behavior of fishers. In coastal areas, however, most recreational fishers remain unmonitored, making it difficult to obtain data on their impact on fish stocks. This is particularly evident in the Venice lagoon, where we conducted a comprehensive study aiming to characterize recreational fishing dynamics. We collected data through interviews, online questionnaires, and remote sensing techniques, including satellite imagery photointerpretation and machine learning algorithms. Our findings reveal spatial and temporal variations in fishing activity, with certain areas and times experiencing higher fishing pressure. This highlights a seasonality in fishing activity and a pattern in fishers’ behaviors that are associated with fish migratory dynamics. Such an association demonstrates the local fishers’ understanding of the fish lifecycle phases and the environmental conditions of the lagoon. Regarding the catch, the most targeted species are seabream (Sparus aurata), seabass (Dicentrarchus labrax), and cuttlefish (Sepia officinalis), with estimated total catches of 18.65 t per year, 15.82 t per year, and 8.36 t per year, respectively. However, our results showed a significant disproportion between the biomass caught by two different groups of fishers that differ in terms of fishing trip frequency, success rate, and catch. While the average catch of the first group, representing most recreational fishers, might be considered of low impact, the catch of the second group, encompassing recreational fishers who fish with very high frequency and efficiency, is substantial in the context of the lagoon ecosystem. Indeed, even considering a conservative estimate, recreational fishing in the Venice lagoon accounted for approximately 2% of the catch of cuttlefish and 17% of the catch of seabream compared to commercial fishing catch, whereas the catch of seabass by recreational fishing approached that of commercial fishing. Therefore, the implementation of a periodic monitoring program utilizing methods such as machine learning algorithms and remote sensing technologies could support the management of recreational fishing dynamics. We also suggest that participatory processes involving both professional and recreational fishers may aid in defining shared approaches and bottom–up initiatives, ensuring enjoyment as well as sustainable uses of coastal areas.

Coasts doi: 10.3390/coasts4030026

Authors: Mark R. Jury Luis E. Alfaro-Garcia

This study analyses climate variability on the north coast of Peru to understand how the local weather is coupled with anomalous ocean conditions. Using high-resolution satellite reanalysis, statistical outcomes are generated via composite analysis and point-to-field regression. Daily time series data for 1979–2023 for Moche area (8S, 79W) river discharge, rainfall, wind, sea surface temperature (SST) and potential evaporation are evaluated for departures from the average. During dry weather in early summer, the southeast Pacific anticyclone expands, an equatorward longshore wind jet ~10 m/s accelerates off northern Peru, and the equatorial trough retreats to 10N. However, most late summers exhibit increased river discharge as local sea temperatures climb above 27 °C, accompanied by 0.5 m/s poleward currents and low salinity. The wet spell composite featured an atmospheric zonal overturning circulation comprised of lower easterly and upper westerly winds > 3 m/s that bring humid air from the Amazon. Convection is aided by diurnal heating and sea breezes that increase the likelihood of rainfall ~ 1 mm/h near sunset. Wet spells in March 2023 were analyzed for synoptic weather forcing and the advection of warm seawater from Ecuador. Although statistical correlations with Moche River discharge indicate a broad zone of equatorial Pacific ENSO forcing (Nino3 R~0.5), the long-range forecast skill is rather modest for February–March rainfall (R2 < 0.2).

Coasts doi: 10.3390/coasts4030025

Authors: Imane Meziane Marc Robin Paul Fattal Oualid Rahmani

This article presents a diachronic study of evolution along the coastline of Noirmoutier Island in France, a sandy shore particularly susceptible to erosion and submersion risks, which are exacerbated by climate change due to two-thirds of its territory being below sea level. The study is based on an analysis of aerial images covering a period of 72 years, divided into five distinct periods: 1950–1974, 1974–1992, 1992–2000, 2000–2010, and 2010–2022. The methodology used combines two complementary approaches: the Digital Shoreline Analysis System (DSAS) for taking linear measurements of the erosion and accretion that have taken place along various shorelines, and the surface method to evaluate the amount of surface lost or gained between different shorelines while calculating the uncertainties associated with the obtained results. The overall trend observed between 1950 and 2022 indicates that the Noirmoutier coastline studied has gained surface area (81 hectares) at an average rate of +0.57 ± 0.06 m per year. The article then presents an application of the method developed by Durand and Heurtefeux in 2006 to estimate the future position of the shoreline. A map of the local area is also provided, identifying the areas susceptible to coastal erosion by 2052 and by 2122, in accordance with the provisions of the Climate and Resilience Law adopted in France on 22 August 2021. The results reveal that there are many sources of uncertainty in predicting the future evolution of the shoreline using this methodology. Therefore, it is crucial to consider these uncertainties when planning future coastal management actions and adopting appropriate adaptation methods to counteract unforeseen developments.

Coasts doi: 10.3390/coasts4030024

Authors: Anushka Egoda Gamage Andrew M. Fischer David S. Nichols Kim Jye Lee Chang

The spatiotemporal distribution of phytoplankton in estuaries is indicative of processes and transport across the land–ocean aquatic continuum (LOAC). Estuaries, as biogeochemically and physically active systems, process large amounts of nutrients and organic matter influencing the transformation of ecological functions. The transformation of the water column drives variation in phytoplankton composition, biomass, and their spatial distribution. Understanding the dynamics of nutrients and organic matter is challenging, yet it provides a comprehensive insight into phytoplankton spatiotemporal distribution across estuaries. Multiple studies have been conducted to understand the spatiotemporal distribution of phytoplankton. Recently, phytoplankton photosynthetic pigments, fatty acids and stable isotopes have been widely used to identify and quantify phytoplankton distribution. This review highlights the use of biogeochemical markers to identify phytoplankton functional groups. It also assesses the current understanding of patterns in the spatiotemporal distribution of phytoplankton and the impact of physical and environmental factors on their distribution in estuaries and coastal oceans. The review will also gather information from in situ sampling studies to evaluate the current state of knowledge and identify gaps.

Coasts doi: 10.3390/coasts4020023

Authors: William A. Gough Zhihui Li

A day-to-day temperature (DTD) variability metric was used to detect marine coastal climates in the province of Ontario, Canada. Eleven of fourteen climate stations on islands, most in the Great Lakes and two in other large water bodies, displayed marine characteristics using a day-to-day temperature metric threshold developed for ocean coastal locations in China and Canada with values below 2.35 for the daily minimum temperature variability. Detailed comparisons with neighbouring coastal stations were conducted for six focal areas in the Great Lakes and the marine effect on the local climate was unambiguously demonstrated in a statistically significant manner. Those displaying marine characteristics were all island climate stations, usually at an elevation close to the lake level, and the marine influence, as measured by day-to-day temperature variability, dropped off rapidly with distance and elevation from the local water body. The DTD metric was compared to a diurnal temperature range (DTR) metric. While DTR was able to distinguish in a statistically significant manner between islands and inland stations, an unambiguous threshold between the two was not possible, unlike DTD.

Coasts doi: 10.3390/coasts4020022

Authors: Daniela Glueck Ulf Schiefelbein Hendrik Schubert

Sand nourishments and groynes as coastal protection measures (CPM) address similar challenges on sandy coasts but take different approaches: while groynes are intended to reduce alongshore sediment transport and erosion, nourishments add new sediment to the system to compensate for erosion. The aim of this study is to compare the ecological effects of such measures on the vegetation. To this end, nutrient analysis and botanical mappings were carried out on a site with installed groynes, a site where sand nourishments are regularly carried out, and a control site without any CPM. In addition to an increase in nutrient availability after the sand nourishment, significant changes in plant species diversity and composition were also measured. The number of higher plants, mosses, and lichen species was lower at the nourishment site. The opposite impacts were observed at the groyne site: an increase in sediment cover by higher plants and mosses and a distinct increase in lichen species. The results suggest that groynes lead to a stabilization of the coastal system and enable dense vegetation growth. In contrast, sand nourishments lead to nutrient input and unstable habitat conditions, attracting certain plant communities but preventing the establishment of ground-covering vegetation.

Coasts doi: 10.3390/coasts4020021

Authors: Jerrica Waddell Christina Pater Michael Coffin Robert Gilmour Simon Courtenay Michael van den Heuvel

Zostera marina is an ecologically valuable species that has been declining due to anthropogenic environmental stressors. In this study, spatial and temporal indicators of eelgrass stress, such as coverage and biomass, were compared with the isotopic composition of C, N, and S to understand the mechanism(s) of plant stress. Eelgrass samples were collected in June, July, and August of 2020 at five stations along an estuary spatial gradient in the southern Gulf of St. Lawrence to measure above- and below-ground biomass and tissue isotopes in eelgrass leaves and roots/rhizomes. Eelgrass biomass was lowest at the innermost sampling station, which coincided with eutrophication-induced hypoxia relative to outer sampling stations. δ13C levels at the upstream station were depleted compared to downstream stations. Comparatively, δ15N and δ34S findings were not correlated with plant biomass. Thus, sulfide intrusion was not a major stressor for eelgrass in this estuary. Between the years 2014 and 2020, eelgrass coverage was found to have increased, which coincided with high and low recorded external nutrient loads from the Wheatley River, respectively. Ultimately, these findings indicate that isotopic composition and biomass can be useful in assessing the health of eelgrass in temperate estuaries.

Coasts doi: 10.3390/coasts4020020

Authors: Gemma Aiello Mauro Caccavale

Some seismo-stratigraphic evidence on the occurrence of wave-cut marine terraces in the Licosa promontory (Southern Tyrrhenian Sea, Italy) based on Sub-bottom Chirp seismic sections is herein presented. Such evidence is provided by marine terraced surfaces situated at various water depths below sea level and etched into the rocky acoustic basement, which are extensively extending in the seaward extension of the Licosa promontory. It is possible that the isotopic stratigraphy and the terraced marine surfaces are connected, so they can be attributed and dated indirectly. The geologic study of seismic profiles has pointed to the prominence of the acoustic basement, extending to the seabed close to the coast and subsiding seawards under the Quaternary marine succession. Ancient remains of marine terraces, found at a range of water depths between 5 m and 50 m, have documented the major morphological changes of the acoustic basement during the Late Quaternary.

Coasts doi: 10.3390/coasts4020019

Authors: James R. Tweedley Stephen J. Beatty Alan Cottingham David L. Morgan Kath Lynch Alan J. Lymbery

Estuaries that become closed from the ocean through the formation of a sand bar are particularly susceptible to degradation and often experience poor water quality and fish kills. Sampling was conducted seasonally for two years in the deeper waters of the Vasse–Wonnerup (southwestern Australia) after a large fish mortality event to identify the fish species present and determine if richness, abundance, diversity and faunal composition differed among regions and over time. Species richness, abundance and diversity were far greater in the downstream regions than in the upstream regions, reflecting patterns in salinity. Catch rates of two marine estuarine-opportunist mugilids (Mugil cephalus and Aldrichetta forsteri) and an estuarine-resident sparid (Acanthopagrus butcheri), which were the species most affected by the mortality event, were relatively stable. It is suggested that before sampling commenced, mugilids had entered the estuary following an artificial sand bar breach, while the loss of 0+ (new recruits) A. butcheri in the mortality event and subsequent recruitment failure prevented stocks from increasing. Temporal shifts in fish composition were driven by less abundant species, which utilized the estuary more opportunistically. Increases in the occurrences and abundances of these species coincided with an open bar and salinities close to those of seawater. The data also show how the estuary responds to differing hydrodynamic phases and artificial breaches.